31. Diketahui 𝑔(𝑥) = 3𝑥 + 2 dan (𝑓 𝑜 𝑔)(𝑥) = 6𝑥 − 4, maka rumus 𝑓(𝑥)= ...
A. 2𝑥 − 14
B. 2𝑥 − 12
C. 2𝑥 − 10
D. 2𝑥 − 8
E. 2𝑥 − 6
Jawaban :
𝑔(𝑥) = 3𝑥 + 2
(𝑓 𝑜 𝑔)(𝑥) = 6𝑥 − 4
f (g (x)) = 6x - 4
f (3x + 2) = 6x - 4
misalkan :
a = 3x + 2
3x = a - 2
x = 1/3 (a - 2)
f (3x + 2) = 6x - 4
f (a) = 6 (1/3 (a - 2)) - 4
f (a) = 2(a - 2) - 4
f (a) = 2a - 4 - 4
f (a) = 2a - 8
maka,
f (x) = 2x - 8
Jawaban : D
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