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Penyelesaian dari pertidaksamaan: scriptbase log invisible function application left parenthesis 2 x plus 5 right parenthesis end scriptbase presuperscript 1 third end presuperscript less than negative 2 adalah ...

  1. x greater than 2

  2. x less than 2

  3. 0 less than x less than 2

  4. x greater than negative 2 , 5

  5. negative 2 , 5 less than x less than 2

Pembahasan Soal:

Ingat pada pertidaksamaan bentuk logaritma jika scriptbase log invisible function application f left parenthesis x right parenthesis end scriptbase presuperscript a less than scriptbase log invisible function application b end scriptbase presuperscript a dan 0 less than a less than 1 maka f open parentheses x close parentheses greater than b greater than 0.

Ingat juga sifat-sifat pada bentuk bentuk logaritma yaitu  

  • scriptbase log invisible function application a end scriptbase presuperscript a equals 1
  • scriptbase log invisible function application b to the power of m end scriptbase presuperscript a equals m times scriptbase log invisible function application b end scriptbase presuperscript a
  • scriptbase log invisible function application b to the power of m end scriptbase presuperscript a to the power of n end presuperscript equals m over n times scriptbase log invisible function application b end scriptbase presuperscript a

Sehingga akan diperoleh

table attributes columnalign right center left columnspacing 0px end attributes row cell scriptbase log invisible function application open parentheses 2 x plus 5 close parentheses end scriptbase presuperscript 1 third end presuperscript end cell less than cell negative 2 end cell row cell scriptbase log invisible function application left parenthesis 2 x plus 5 right parenthesis end scriptbase presuperscript 3 to the power of negative 1 end exponent end presuperscript end cell less than cell negative 2 times scriptbase log invisible function application 3 end scriptbase presuperscript 3 end cell row cell negative 1 times scriptbase log invisible function application left parenthesis 2 x plus 5 right parenthesis end scriptbase presuperscript 3 end cell less than cell negative 2 times scriptbase log invisible function application 3 end scriptbase presuperscript 3 end cell row cell scriptbase log invisible function application left parenthesis 2 x plus 5 right parenthesis to the power of negative 1 end exponent end scriptbase presuperscript 3 end cell less than cell scriptbase log invisible function application open parentheses 3 close parentheses to the power of negative 2 end exponent end scriptbase presuperscript 3 end cell row cell left parenthesis 2 x plus 5 right parenthesis to the power of negative 1 end exponent end cell less than cell open parentheses 3 close parentheses to the power of negative 2 end exponent end cell row cell left parenthesis 2 x plus 5 right parenthesis to the power of 1 end cell greater than cell open parentheses 3 close parentheses squared end cell row cell 2 x plus 5 end cell greater than 9 row cell 2 x end cell greater than cell 9 minus 5 end cell row cell 2 x end cell greater than 4 row x greater than cell 4 over 2 end cell row x greater than 2 end table

Karena syarat numerus pada bentuk logaritma scriptbase log invisible function application b end scriptbase presuperscript a yaitu b greater than 0, maka

table attributes columnalign right center left columnspacing 0px end attributes row cell 2 x plus 5 end cell greater than 0 row cell 2 x end cell greater than cell negative 5 end cell row x greater than cell fraction numerator negative 5 over denominator 2 end fraction end cell row x greater than cell negative 2 , 5 end cell end table

Dari hasil di atas maka penyelesainnya yaitu irisan dari x greater than 2 dan x greater than negative 2 , 5 yaitu x greater than 2

Jadi, dapat disimpulkan bahwa penyelesaian dari pertidaksamaan scriptbase log invisible function application left parenthesis 2 x plus 5 right parenthesis end scriptbase presuperscript 1 third end presuperscript less than negative 2 adalah x greater than 2.

Oleh karena itu, jawaban yang benar adalah A.

Pembahasan terverifikasi oleh Roboguru

Dijawab oleh:

M. Iqbal

Mahasiswa/Alumni Universitas Negeri Semarang

Terakhir diupdate 11 Juli 2021

Roboguru sudah bisa jawab 91.4% pertanyaan dengan benar

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Pertanyaan yang serupa

Nilai yang memenuhi pertidaksamaan:  adalah ...

Pembahasan Soal:

Ingat pada pertidaksamaan bentuk logaritma jika scriptbase log invisible function application f left parenthesis x right parenthesis end scriptbase presuperscript a greater than scriptbase log invisible function application b end scriptbase presuperscript a dan 0 less than a less than 1 maka 0 less than f open parentheses x close parentheses less than b.

Ingat juga sifat-sifat pada bentuk bentuk logaritma yaitu  

  • scriptbase log invisible function application a end scriptbase presuperscript a equals 1
  • scriptbase log invisible function application b to the power of m end scriptbase presuperscript a equals m times scriptbase log invisible function application b end scriptbase presuperscript a
  • scriptbase log invisible function application b to the power of m end scriptbase presuperscript a to the power of n end presuperscript equals m over n times scriptbase log invisible function application b end scriptbase presuperscript a

Sehingga akan diperoleh

table attributes columnalign right center left columnspacing 0px end attributes row cell scriptbase log invisible function application open parentheses x squared minus 1 close parentheses end scriptbase presuperscript 0 , 1 end presuperscript end cell greater than 2 row cell scriptbase log invisible function application left parenthesis x squared minus 1 right parenthesis end scriptbase presuperscript 1 over 10 end presuperscript end cell greater than cell 2 times scriptbase log invisible function application 10 end scriptbase presuperscript 10 end cell row cell scriptbase log invisible function application left parenthesis x squared minus 1 right parenthesis end scriptbase presuperscript 10 to the power of negative 1 end exponent end presuperscript end cell greater than cell scriptbase log invisible function application 10 squared end scriptbase presuperscript 10 end cell row cell negative 1 times scriptbase log invisible function application left parenthesis x squared minus 1 right parenthesis end scriptbase presuperscript 10 end cell greater than cell scriptbase log invisible function application 100 end scriptbase presuperscript 10 end cell row cell scriptbase log invisible function application left parenthesis x squared minus 1 right parenthesis to the power of negative 1 end exponent end scriptbase presuperscript 10 end cell greater than cell scriptbase log invisible function application 100 end scriptbase presuperscript 10 end cell row cell left parenthesis x squared minus 1 right parenthesis to the power of negative 1 end exponent end cell greater than 100 row cell left parenthesis x squared minus 1 right parenthesis to the power of 1 end cell less than cell 100 to the power of negative 1 end exponent end cell row cell x squared minus 1 end cell less than cell 1 over 100 end cell row cell x squared minus 1 end cell less than cell 0 , 01 end cell row cell x squared end cell less than cell 0 , 01 plus 1 end cell row cell x squared end cell less than cell 1 , 01 end cell row x less than cell square root of 1 , 01 end root end cell row x less than cell plus-or-minus square root of 1 , 01 end root end cell end table

Didapatkan x less than square root of 1 , 01 end root atau x greater than negative square root of 1 , 01 end root.

Karena syarat numerus pada bentuk logaritma scriptbase log invisible function application b end scriptbase presuperscript a yaitu b greater than 0, maka

table attributes columnalign right center left columnspacing 0px end attributes row cell x squared minus 1 end cell greater than 0 row cell x squared end cell greater than 1 row x greater than cell square root of 1 end cell row x greater than cell plus-or-minus 1 end cell end table

Didapatkan x greater than 1 dan x less than negative 1

Dari hasil di atas maka penyelesainnya yaitu irisan dari x less than square root of 1 , 01 end rootx greater than negative square root of 1 , 01 end rootx greater than 1, dan x less than negative 1 yaitu negative square root of 1 , 01 end root less than x less than negative 1 atau 1 less than x less than square root of 1 , 01 end root.

Jadi, dapat disimpulkan bahwa nilai x yang memenuhi pertidaksamaan: scriptbase log invisible function application left parenthesis x squared minus 1 right parenthesis end scriptbase presuperscript 0 , 1 end presuperscript greater than 2 adalah negative square root of 1 , 01 end root less than x less than negative 1 atau 1 less than x less than square root of 1 , 01 end root.

Oleh karena itu, jawaban yang benar adalah D.

0

Roboguru

Nilai yang memenuhi pertidaksamaan:  adalah ...

Pembahasan Soal:

Ingat pada pertidaksamaan bentuk logaritma jika scriptbase log invisible function application f left parenthesis x right parenthesis end scriptbase presuperscript a less than scriptbase log invisible function application b end scriptbase presuperscript a dan a greater than 0 maka 0 less than f left parenthesis x right parenthesis less than b.

Ingat juga sifat-sifat pada bentuk bentuk logaritma yaitu  

  • scriptbase log invisible function application a end scriptbase presuperscript a equals 1
  • scriptbase log invisible function application b to the power of m end scriptbase presuperscript a equals m times scriptbase log invisible function application b end scriptbase presuperscript a

Sehingga akan diperoleh

table attributes columnalign right center left columnspacing 0px end attributes row cell scriptbase log invisible function application open parentheses 2 x plus 4 close parentheses end scriptbase presuperscript 2 end cell less than 3 row cell scriptbase log invisible function application left parenthesis 2 x plus 4 right parenthesis end scriptbase presuperscript 2 end cell less than cell 3 times scriptbase log invisible function application 2 end scriptbase presuperscript 2 end cell row cell scriptbase log invisible function application left parenthesis 2 x plus 4 right parenthesis end scriptbase presuperscript 2 end cell less than cell scriptbase log invisible function application 2 cubed end scriptbase presuperscript 2 end cell row cell scriptbase log invisible function application left parenthesis 2 x plus 4 right parenthesis end scriptbase presuperscript 2 end cell less than cell scriptbase log invisible function application 8 end scriptbase presuperscript 2 end cell row cell 2 x plus 4 end cell less than 8 row cell 2 x end cell less than cell 8 minus 4 end cell row cell 2 x end cell less than 4 row x less than 2 end table

Karena syarat numerus pada bentuk logaritma scriptbase log invisible function application b end scriptbase presuperscript a yaitu b greater than 0, maka

table attributes columnalign right center left columnspacing 0px end attributes row cell 2 x plus 4 end cell greater than 0 row cell 2 x end cell greater than cell negative 4 end cell row x greater than cell fraction numerator negative 4 over denominator 2 end fraction end cell row x greater than cell negative 2 end cell end table

Dari hasil di atas maka penyelesainnya yaitu irisan dari x less than 2 dan x greater than negative 2 yaitu negative 2 less than x less than 2.

Jadi, dapat disimpulkan bahwa nilai x yang memenuhi pertidaksamaan: scriptbase log invisible function application left parenthesis 2 x plus 4 right parenthesis end scriptbase presuperscript 2 less than 3 adalah negative 2 less than x less than 2.

Oleh karena itu, jawaban yang benar adalah D.

1

Roboguru

Akar-akar dari  adalah  dan  maka

Pembahasan Soal:

Ingat sifat pada persamaan bentuk logaritma yaitu scriptbase log invisible function application f left parenthesis x right parenthesis end scriptbase presuperscript a equals scriptbase log invisible function application g left parenthesis x right parenthesis end scriptbase presuperscript b rightwards arrow f open parentheses x close parentheses equals g left parenthesis x right parenthesis dan sifat pada bentuk logaritma yaitu

  • scriptbase log invisible function application a end scriptbase presuperscript a equals 1
  • scriptbase log invisible function application b end scriptbase presuperscript a plus scriptbase log invisible function application c end scriptbase presuperscript a equals scriptbase log invisible function application b c end scriptbase presuperscript a
  • scriptbase log invisible function application b to the power of m end scriptbase presuperscript a to the power of n end presuperscript equals m over n times scriptbase log invisible function application b end scriptbase presuperscript a
  • scriptbase log invisible function application b to the power of m end scriptbase presuperscript a equals m times scriptbase log invisible function application b end scriptbase presuperscript a

Ingat syarat basis pada logaritma scriptbase log invisible function application b end scriptbase presuperscript a yaitu a greater than 0 dan a not equal to 1 dan syarat numerus pada logaritma scriptbase log invisible function application b end scriptbase presuperscript a yaitu b greater than 0. Sehingga

table attributes columnalign right center left columnspacing 0px end attributes row cell scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 end cell equals cell 1 plus scriptbase log invisible function application left parenthesis x minus 1 right parenthesis end scriptbase presuperscript 9 end cell row cell scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 end cell equals cell scriptbase log invisible function application 3 end scriptbase presuperscript 3 plus scriptbase log invisible function application left parenthesis x minus 1 right parenthesis end scriptbase presuperscript 3 squared end presuperscript end cell row cell scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 end cell equals cell scriptbase log invisible function application 3 end scriptbase presuperscript 3 plus 1 half scriptbase log invisible function application left parenthesis x minus 1 right parenthesis end scriptbase presuperscript 3 end cell row cell scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 end cell equals cell scriptbase log invisible function application 3 end scriptbase presuperscript 3 plus scriptbase log invisible function application open parentheses left parenthesis x minus 1 right parenthesis to the power of 1 half end exponent close parentheses end scriptbase presuperscript 3 end cell row cell scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 end cell equals cell scriptbase log invisible function application open parentheses 3 times left parenthesis x minus 1 right parenthesis to the power of 1 half end exponent close parentheses end scriptbase presuperscript 3 end cell row cell x plus 1 end cell equals cell 3 times left parenthesis x minus 1 right parenthesis to the power of 1 half end exponent end cell row cell open parentheses x plus 1 close parentheses squared end cell equals cell open parentheses 3 times left parenthesis x minus 1 right parenthesis to the power of 1 half end exponent close parentheses squared end cell row cell x squared plus 2 x plus 1 end cell equals cell 3 squared times left parenthesis x minus 1 right parenthesis end cell row cell x squared plus 2 x plus 1 end cell equals cell 9 times left parenthesis x minus 1 right parenthesis end cell row cell x squared plus 2 x plus 1 end cell equals cell 9 x minus 9 end cell row cell x squared plus 2 x minus 9 x plus 1 plus 9 end cell equals 0 row cell x squared minus 7 x plus 10 end cell equals 0 row cell left parenthesis x minus 2 right parenthesis left parenthesis x minus 5 right parenthesis end cell equals 0 row cell x minus 2 end cell equals cell 0 blank atau blank x minus 5 equals 0 end cell row x equals cell 2 blank atau blank x equals 5 end cell end table

Didapatkan akar-akar dari persamaan tersebut yaitu x subscript 1 equals 2 dan x equals 5. Maka nilai dari x subscript 1 plus x subscript 2 sebagai berikut.

table attributes columnalign right center left columnspacing 0px end attributes row cell x subscript 1 plus x subscript 2 end cell equals cell 2 plus 5 end cell row blank equals 7 end table

Jadi, dapat disimpulkan bahwa nilai dari x subscript 1 plus x subscript 2 adalah 7.

Oleh karena itu, jawaban yang benar adalah D.

0

Roboguru

Misal persamaan logaritma:  mempunyai akar-akar  dan  maka

Pembahasan Soal:

Ingat materi persamaan logaritma dengan basisnya adalah fungsi yang berbeda dan numerusnya adalah fungsi yang sama dan bentuk umum atau definisi dari logaritma yaitu scriptbase log invisible function application b end scriptbase presuperscript a equals c rightwards arrow a to the power of c equals b.

Ingat juga sifat-sifat pada bentuk logaritma yaitu 

  • scriptbase log invisible function application a end scriptbase presuperscript a equals 1
  • scriptbase log invisible function application b to the power of m end scriptbase presuperscript a equals m times scriptbase log invisible function application b end scriptbase presuperscript a
  • scriptbase log invisible function application b to the power of m end scriptbase presuperscript a to the power of n end presuperscript equals m over n times scriptbase log invisible function application b end scriptbase presuperscript a

Untuk menyelesaikan persamaan tersebut maka dilakkukan permisalan terlebih dahulu.

Misalkan scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 equals y sehingga

table attributes columnalign right center left columnspacing 0px end attributes row cell scriptbase log invisible function application open parentheses x plus 1 close parentheses end scriptbase presuperscript 3 plus fraction numerator 3 over denominator scriptbase log invisible function application open parentheses x plus 1 close parentheses end scriptbase presuperscript 9 end fraction end cell equals 5 row cell scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 plus fraction numerator 3 over denominator scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 squared end presuperscript end fraction end cell equals 5 row cell scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 plus fraction numerator 3 over denominator 1 half times scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 end fraction end cell equals 5 row cell y plus fraction numerator 3 over denominator 1 half times y end fraction end cell equals 5 row cell y plus 6 over y end cell equals 5 row cell y squared plus 6 end cell equals cell 5 y end cell row cell y squared minus 5 y plus 6 end cell equals 0 row cell left parenthesis y minus 2 right parenthesis left parenthesis y minus 3 right parenthesis end cell equals 0 row cell y minus 2 end cell equals cell 0 blank atau blank y minus 3 equals 0 end cell row y equals cell 2 blank atau blank y equals 3 end cell end table

Didapatkan hasil y subscript 1 equals 2 dan y subscript 2 equals 3, maka

table attributes columnalign right center left columnspacing 0px end attributes row cell y subscript 1 end cell equals 2 row cell scriptbase log space invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 end cell equals 2 row cell 3 squared end cell equals cell x plus 1 end cell row 9 equals cell x plus 1 end cell row cell 9 minus 1 end cell equals x row 8 equals x end table

table attributes columnalign right center left columnspacing 0px end attributes row cell y subscript 2 end cell equals 3 row cell scriptbase log space invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 end cell equals 3 row cell 3 cubed end cell equals cell x plus 1 end cell row 27 equals cell x plus 1 end cell row cell 27 minus 1 end cell equals x row 26 equals x end table

Didapatkan hasil x subscript 1 equals 8 dan x subscript 2 equals 26, sehingga hasil dari x subscript 1 plus x subscript 2 adalah

table attributes columnalign right center left columnspacing 0px end attributes row cell x subscript 1 plus x subscript 2 end cell equals cell 8 plus 26 end cell row blank equals 34 end table

Jadi, dapat disimpulkan bahwa persamaan logaritma: scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 3 plus fraction numerator 3 over denominator scriptbase log invisible function application left parenthesis x plus 1 right parenthesis end scriptbase presuperscript 9 end fraction equals 5 mempunyai akar-akar x subscript 1 dan x subscript 2 maka x subscript 1 plus x subscript 2 equals 34.

Oleh karena itu, jawaban yang benar adalah A.

0

Roboguru

Tentukan himpunan penyelesaian pertidaksamaan berikut. b.

Pembahasan Soal:

Ingat sifat-sifat bentuk logaritma:

log presuperscript a space a to the power of n equals n 

Pada pertidaksamaan logaritma untuk 0 less than a less than 1 jika:

log presuperscript a space f open parentheses x close parentheses less or equal than log presuperscript a space g open parentheses x close parentheses rightwards arrow f open parentheses x close parentheses greater or equal than g open parentheses x close parentheses comma space f open parentheses x close parentheses greater than 0 comma space dan space g open parentheses x close parentheses greater than 0 

Diketahui log presuperscript begin inline style 1 half end style end presuperscript space open parentheses x squared minus 2 x plus 1 close parentheses less or equal than negative 4 maka:

table attributes columnalign right center left columnspacing 0px end attributes row cell log presuperscript begin inline style 1 half end style end presuperscript space open parentheses x squared minus 2 x plus 1 close parentheses end cell less or equal than cell negative 4 end cell row cell log presuperscript begin inline style 1 half end style end presuperscript space space open parentheses x squared minus 2 x plus 1 close parentheses end cell less or equal than cell log presuperscript begin inline style 1 half end style end presuperscript space open parentheses 1 half close parentheses to the power of negative 4 end exponent end cell row cell x squared minus 2 x plus 1 end cell greater or equal than cell open parentheses 2 to the power of negative 1 end exponent close parentheses to the power of negative 4 end exponent end cell row cell x squared minus 2 x plus 1 end cell greater or equal than cell 2 to the power of 4 end cell row cell x squared minus 2 x plus 1 end cell greater or equal than 16 row cell x squared minus 2 x plus 1 minus 16 end cell greater or equal than 0 row cell x squared minus 2 x minus 15 end cell greater or equal than 0 row cell open parentheses x minus 5 close parentheses open parentheses x plus 3 close parentheses end cell greater or equal than 0 end table 

sehingga nilai yang memenuhi x less or equal than negative 3 atau x greater or equal than 5.

 syarat numerus:

table attributes columnalign right center left columnspacing 0px end attributes row cell x squared minus 2 x plus 1 end cell greater than 0 row cell open parentheses x minus 1 close parentheses open parentheses x minus 1 close parentheses end cell greater than 0 row x greater than 1 end table 

Dari syarat numerus mengharuskan x greater than 1, maka yang memenuhi adalah x greater or equal than 5

Dengan demikian himpunan penyelesaian pertidaksamaan tersebut adalah open curly brackets x vertical line x greater or equal than 5 comma space x element of straight R close curly brackets.

0

Roboguru

Roboguru sudah bisa jawab 91.4% pertanyaan dengan benar

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