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DIketahui  dan . Nilai  = ...

Pertanyaan

DIketahui left parenthesis f ring operator g right parenthesis left parenthesis x right parenthesis equals 4 x squared plus 8 x minus 3 dan g left parenthesis x right parenthesis equals 2 x plus 4. Nilai f left parenthesis negative 2 right parenthesis = ...

  1. negative 15 

  2. negative 9 

  3. negative 7 

  4. 1 

  5. 9 

Pembahasan Soal:

Diketahui : left parenthesis f ring operator g right parenthesis left parenthesis x right parenthesis equals 4 x squared plus 8 x minus 3g left parenthesis x right parenthesis equals 2 x plus 4 

Misal table attributes columnalign right center left columnspacing 0px end attributes row cell 2 x plus 4 end cell equals y end table 

table attributes columnalign right center left columnspacing 0px end attributes row cell 2 x plus 4 end cell equals y row cell 2 x end cell equals cell y minus 4 end cell row x equals cell fraction numerator y minus 4 over denominator 2 end fraction end cell end table 

table attributes columnalign right center left columnspacing 0px end attributes row cell left parenthesis f ring operator g right parenthesis left parenthesis x right parenthesis end cell equals cell 4 x squared plus 8 x minus 3 end cell row cell f left parenthesis g left parenthesis x right parenthesis right parenthesis end cell equals cell 4 x squared plus 8 x minus 3 end cell row cell f left parenthesis 2 x plus 4 right parenthesis end cell equals cell 4 x squared plus 8 x minus 3 end cell end table 

Substitusikan nilai x

f left parenthesis y right parenthesis equals 4 left parenthesis fraction numerator y minus 4 over denominator 2 end fraction right parenthesis squared plus 8 left parenthesis fraction numerator y minus 4 over denominator 2 end fraction right parenthesis minus 3 f left parenthesis y right parenthesis equals 4 left parenthesis fraction numerator y squared minus 8 y plus 16 over denominator 4 end fraction right parenthesis plus 4 left parenthesis y minus 4 right parenthesis minus 3 f left parenthesis y right parenthesis equals y squared minus 8 y plus 16 plus 4 y minus 16 minus 3 f left parenthesis y right parenthesis equals y squared minus 4 y minus 3 f left parenthesis x right parenthesis equals x squared minus 4 x minus 3  

maka

table attributes columnalign right center left columnspacing 0px end attributes row cell f left parenthesis negative 2 right parenthesis end cell equals cell left parenthesis negative 2 right parenthesis squared minus 4 left parenthesis negative 2 right parenthesis minus 3 end cell row blank equals cell 4 plus 8 minus 3 end cell row blank equals 9 end table 

 Oleh karena itu, jawaban yang benar adalah E. 

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 04 Mei 2021

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