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Pertanyaan

Diketahui f ( x ) = x + 3 54 ​ dan g ( x ) = 2 x + 7 , tentukan : a. ( f ∘ g ) ( x ) dan ( g ∘ f ) − 1 ( x ) b. Jika f ( a ) = a carilah nilai

Diketahui  dan , tentukan :

a.  dan 

b. Jika  carilah nilai a

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M. Iqbal

Master Teacher

Mahasiswa/Alumni Universitas Negeri Semarang

Jawaban terverifikasi

Jawaban

dapat disimpulkan bahwa didapatkan hasil yaitu , yaitu dan .

dapat disimpulkan bahwa didapatkan hasil open parentheses f ring operator g close parentheses open parentheses x close parentheses yaitu table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell fraction numerator 54 over denominator 2 x plus 10 end fraction end cell end tableopen parentheses g ring operator f close parentheses to the power of negative 1 end exponent open parentheses x close parentheses yaitu table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell fraction numerator negative 3 x plus 129 over denominator x minus 7 end fraction end cell end table dan table attributes columnalign right center left columnspacing 0px end attributes row a equals cell 6 space atau space a equals negative 9 end cell end table.

Pembahasan

Ingat rumus umum untuk fungsi komposisi serta invers fungsi yaitu Misalkan fungsi yang memetakan ke , sehingga bisa kita tulisakan menjadi , maka merupakan fungsi yang memetakan ke , ditulis Fungsi komposisi didapatkan dengan mensubtitusikan fungsi ke dalam nilai Maka, Menentukan hasil dari Maka Menentukan Maka, Menentukan nilai Maka, Jadi, dapat disimpulkan bahwa didapatkan hasil yaitu , yaitu dan .

Ingat rumus umum untuk fungsi komposisi serta invers fungsi yaitu 

  • left parenthesis f ring operator g right parenthesis left parenthesis x right parenthesis equals f left square bracket g left parenthesis x right parenthesis right square bracket
  • left parenthesis g ring operator f right parenthesis left parenthesis x right parenthesis equals g left square bracket f left parenthesis x right parenthesis right square bracket
  • Misalkan f fungsi yang memetakan x ke y, sehingga bisa kita tulisakan menjadi y equals f left parenthesis x right parenthesis, maka f to the power of negative 1 end exponent merupakan fungsi yang memetakan y ke x, ditulis x equals f to the power of negative 1 end exponent left parenthesis y right parenthesis

Fungsi komposisi didapatkan dengan mensubtitusikan fungsi ke dalam nilai x

table attributes columnalign right center left columnspacing 0px end attributes row cell open parentheses f ring operator g close parentheses open parentheses x close parentheses end cell equals cell f left square bracket g left parenthesis x right parenthesis right square bracket end cell row blank equals cell f left square bracket 2 x plus 7 right square bracket end cell row blank equals cell fraction numerator 54 over denominator 2 x plus 7 plus 3 end fraction end cell row blank equals cell fraction numerator 54 over denominator 2 x plus 10 end fraction end cell end table

Maka, table attributes columnalign right center left columnspacing 0px end attributes row cell open parentheses f ring operator g close parentheses open parentheses x close parentheses end cell equals cell fraction numerator 54 over denominator 2 x plus 10 end fraction end cell end table

Menentukan hasil dari open parentheses g ring operator f close parentheses to the power of negative 1 end exponent open parentheses x close parentheses

table attributes columnalign right center left columnspacing 0px end attributes row cell open parentheses g ring operator f close parentheses open parentheses x close parentheses end cell equals cell g left square bracket f left parenthesis x right parenthesis right square bracket end cell row blank equals cell g open square brackets fraction numerator 54 over denominator x plus 3 end fraction close square brackets end cell row blank equals cell 2 open parentheses fraction numerator 54 over denominator x plus 3 end fraction close parentheses plus 7 end cell row blank equals cell fraction numerator 108 over denominator x plus 3 end fraction plus 7 end cell row blank equals cell fraction numerator 108 over denominator x plus 3 end fraction plus fraction numerator 7 left parenthesis x plus 3 right parenthesis over denominator x plus 3 end fraction end cell row blank equals cell fraction numerator 108 over denominator x plus 3 end fraction plus fraction numerator 7 x plus 21 over denominator x plus 3 end fraction end cell row blank equals cell fraction numerator 7 x plus 129 over denominator x plus 3 end fraction end cell end table

Maka left parenthesis g ring operator f right parenthesis left parenthesis x right parenthesis equals fraction numerator 7 x plus 129 over denominator x plus 3 end fraction

Menentukan open parentheses g ring operator f close parentheses to the power of negative 1 end exponent open parentheses x close parentheses

table attributes columnalign right center left columnspacing 0px end attributes row cell left parenthesis g ring operator f right parenthesis left parenthesis x right parenthesis end cell equals cell fraction numerator 7 x plus 129 over denominator x plus 3 end fraction end cell row y equals cell fraction numerator 7 x plus 129 over denominator x plus 3 end fraction end cell row cell y left parenthesis x plus 3 right parenthesis end cell equals cell 7 x plus 129 end cell row cell x y minus 7 x end cell equals cell negative 3 y plus 129 end cell row cell x left parenthesis y minus 7 right parenthesis end cell equals cell negative 3 y plus 129 end cell row x equals cell fraction numerator negative 3 y plus 129 over denominator y minus 7 end fraction end cell row cell left parenthesis g ring operator f right parenthesis to the power of negative 1 end exponent left parenthesis y right parenthesis end cell equals cell fraction numerator negative 3 y plus 129 over denominator y minus 7 end fraction end cell row cell left parenthesis g ring operator f right parenthesis to the power of negative 1 end exponent left parenthesis x right parenthesis end cell equals cell fraction numerator negative 3 x plus 129 over denominator x minus 7 end fraction end cell end table

Maka, table attributes columnalign right center left columnspacing 0px end attributes row cell open parentheses g ring operator f close parentheses to the power of negative 1 end exponent open parentheses x close parentheses end cell equals cell fraction numerator negative 3 x plus 129 over denominator x minus 7 end fraction end cell end table

Menentukan nilai a

table attributes columnalign right center left columnspacing 0px end attributes row cell f left parenthesis x right parenthesis end cell equals cell fraction numerator 54 over denominator x plus 3 end fraction end cell row cell f left parenthesis a right parenthesis end cell equals cell fraction numerator 54 over denominator a plus 3 end fraction end cell row a equals cell fraction numerator 54 over denominator a plus 3 end fraction end cell row cell a left parenthesis a plus 3 right parenthesis end cell equals 54 row cell a squared plus 3 a end cell equals 54 row cell a squared plus 3 a minus 54 end cell equals 0 row cell left parenthesis a minus 6 right parenthesis left parenthesis a plus 9 right parenthesis end cell equals 0 row a equals cell 6 space atau end cell row a equals cell negative 9 end cell end table

Maka, table attributes columnalign right center left columnspacing 0px end attributes row a equals cell 6 space atau space a equals negative 9 end cell end table

Jadi, dapat disimpulkan bahwa didapatkan hasil open parentheses f ring operator g close parentheses open parentheses x close parentheses yaitu table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell fraction numerator 54 over denominator 2 x plus 10 end fraction end cell end tableopen parentheses g ring operator f close parentheses to the power of negative 1 end exponent open parentheses x close parentheses yaitu table attributes columnalign right center left columnspacing 0px end attributes row blank blank cell fraction numerator negative 3 x plus 129 over denominator x minus 7 end fraction end cell end table dan table attributes columnalign right center left columnspacing 0px end attributes row a equals cell 6 space atau space a equals negative 9 end cell end table.

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