Question

25. Diketahui fungsi f(x) = 2/3 x +b. Jika f(b) = b+2, nilai f(-b)= .........

A. -5
B. -2
C. 1
D. 3

(HARUS PAKAI CARA....!!!

Answer 1

F(x) = 2/3x+b
f(b) = b+2
2/3b+b = b+2
2/3b+b-b = 2
2/3b = 2
2b = 6
b = 3

f(-b) = f(-3)
       = 2/3(-3) + 3
       = -2+3
       = 1
jawab: C

Answer 2

F(x) = (2/3)x + b
f(b) = b + 2
b + 2 = (2/3)b + b
b + 2 = (5/3)b
b - (5/3)b = - 2
(-2/3)b = - 2
b = 3

f(x) = (2/3)x + 3
f(-b) = f(-3) = (2/3)(-3) + 3
                = - 2 + 3
               = 1