Suatu fungsi f(x) =4x-1;f(a) =-9 dan f(2)=b nilai a-b adalah A. -9 B. -5 C. 5 D. 9

f(x) = 4x-1
f(a) = 4a-1
-9 = 4a-1
4a = -8
a = -2

f(2) = 4(2)-1
b = 8-1
b = 7

maka, a-b = -2-7 = -9

Jawaban : A
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