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Diberikan f ( x ) = − k x − 1 2 k ​ dan g ( x ) = 2 x + 6 ​ . Jika ( 5 g 2 ⋅ f ) ( − 2 ) = 15 ,maka nilai dari 2 k − 5 adalah ....

Diberikan  dan . Jika , maka nilai dari  adalah ....

  1. begin mathsize 14px style negative 11 end style

  2. begin mathsize 14px style negative 8 end style

  3. size 14px minus size 14px 19 over size 14px 3

  4. size 14px minus size 14px 11 over size 14px 3 

  5. begin mathsize 14px style 8 end style 

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I. Roy

Master Teacher

Mahasiswa/Alumni Universitas Negeri Surabaya

Jawaban terverifikasi

Jawaban

jawabannyaadalahB.

jawabannya adalah B.

Pembahasan

Ingat kembali bahwa . Sehingga Substitusikan , maka . Akan dicari nilai dari dan terlebihdahulu. Perhatikan bahwa nilai dari adalah sebagai berikut. dan nilai dari adalah sebagai berikut. Maka, diperoleh Sehingga didapat Jadi, jawabannyaadalahB.

Ingat kembali bahwa begin mathsize 14px style left parenthesis g times f right parenthesis left parenthesis x right parenthesis equals g left parenthesis x right parenthesis times f left parenthesis x right parenthesis end style. Sehingga

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell left parenthesis 5 g squared times f right parenthesis left parenthesis x right parenthesis end cell equals cell left parenthesis 5 g times g times f right parenthesis left parenthesis x right parenthesis end cell row blank equals cell 5 times g left parenthesis x right parenthesis times g left parenthesis x right parenthesis times f left parenthesis x right parenthesis end cell end table end style

Substitusikan size 14px x size 14px equals size 14px minus size 14px 2, maka

size 14px left parenthesis size 14px 5 size 14px g to the power of size 14px 2 size 14px times size 14px f size 14px right parenthesis begin mathsize 14px style left parenthesis negative 2 right parenthesis end style size 14px equals size 14px 5 size 14px times size 14px g begin mathsize 14px style left parenthesis negative 2 right parenthesis end style size 14px times size 14px g begin mathsize 14px style left parenthesis negative 2 right parenthesis end style size 14px times size 14px f begin mathsize 14px style left parenthesis negative 2 right parenthesis end style.

Akan dicari nilai dari  begin mathsize 14px style f left parenthesis negative 2 right parenthesis end style dan  begin mathsize 14px style g left parenthesis negative 2 right parenthesis end style terlebih dahulu.

Perhatikan bahwa nilai dari begin mathsize 14px style f left parenthesis negative 2 right parenthesis end style adalah sebagai berikut.

table attributes columnalign right center left columnspacing 0px end attributes row cell size 14px f begin mathsize 14px style left parenthesis negative 2 right parenthesis end style end cell size 14px equals cell size 14px minus fraction numerator size 14px 2 size 14px k over denominator size 14px k begin mathsize 14px style left parenthesis negative 2 right parenthesis end style size 14px minus size 14px 1 end fraction end cell row blank size 14px equals cell size 14px minus fraction numerator size 14px 2 size 14px k over denominator size 14px minus size 14px 2 size 14px k size 14px minus size 14px 1 end fraction end cell row blank size 14px equals cell fraction numerator size 14px 2 size 14px k over denominator size 14px 2 size 14px k size 14px plus size 14px 1 end fraction end cell end table

dan nilai dari undefined adalah sebagai berikut.

table attributes columnalign right center left columnspacing 0px end attributes row cell size 14px g begin mathsize 14px style left parenthesis negative 2 right parenthesis end style end cell size 14px equals cell square root of size 14px 2 begin mathsize 14px style left parenthesis negative 2 right parenthesis end style size 14px plus size 14px 6 end root end cell row blank size 14px equals cell square root of size 14px minus size 14px 4 size 14px plus size 14px 6 end root end cell row blank size 14px equals cell square root of size 14px 2 end cell end table 

Maka, diperoleh

table attributes columnalign right center left columnspacing 0px end attributes row cell size 14px left parenthesis size 14px 5 size 14px g to the power of size 14px 2 size 14px times size 14px f size 14px right parenthesis begin mathsize 14px style left parenthesis negative 2 right parenthesis end style end cell size 14px equals cell size 14px 5 size 14px times size 14px g begin mathsize 14px style left parenthesis negative 2 right parenthesis end style size 14px times size 14px g begin mathsize 14px style left parenthesis negative 2 right parenthesis end style size 14px times size 14px f begin mathsize 14px style left parenthesis negative 2 right parenthesis end style end cell row size 14px 15 size 14px equals cell size 14px 5 begin mathsize 14px style left parenthesis square root of 2 right parenthesis end style begin mathsize 14px style left parenthesis square root of 2 right parenthesis end style begin mathsize 14px style left parenthesis fraction numerator 2 k over denominator 2 k plus 1 end fraction right parenthesis end style end cell row size 14px 15 size 14px equals cell size 14px 5 size 14px times size 14px 2 begin mathsize 14px style left parenthesis fraction numerator 2 k over denominator 2 k plus 1 end fraction right parenthesis end style end cell row size 14px 3 size 14px equals cell size 14px 2 begin mathsize 14px style left parenthesis fraction numerator 2 k over denominator 2 k plus 1 end fraction right parenthesis end style end cell row cell size 14px 3 begin mathsize 14px style left parenthesis 2 k plus 1 right parenthesis end style end cell size 14px equals cell size 14px 2 size 14px times size 14px 2 size 14px k end cell row cell size 14px 6 size 14px k size 14px plus size 14px 3 end cell size 14px equals cell size 14px 4 size 14px k end cell row cell size 14px 6 size 14px k size 14px minus size 14px 4 size 14px k end cell size 14px equals cell size 14px minus size 14px 3 end cell row cell size 14px 2 size 14px k end cell size 14px equals cell size 14px minus size 14px 3 end cell row size 14px k size 14px equals cell size 14px minus size 14px 3 over size 14px 2 end cell end table 

Sehingga didapat

table attributes columnalign right center left columnspacing 0px end attributes row cell size 14px 2 size 14px k size 14px minus size 14px 5 end cell size 14px equals cell size 14px 2 begin mathsize 14px style left parenthesis negative 3 over 2 right parenthesis end style size 14px minus size 14px 5 end cell row blank size 14px equals cell size 14px minus size 14px 3 size 14px minus size 14px 5 end cell row blank size 14px equals cell size 14px minus size 14px 8 end cell end table 

Jadi, jawabannya adalah B.

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