Diketahui rumus fungsi f(2x + 3)= 6x + 8, nilai f(7) adalah..... A. 10 B. 16 C. 12 D. 20

Bab Fungsi
Matematika SMA Kelas XI

2x + 3 = 7
2x = 7 - 3
x = 4 : 2
x = 2

→ 6x + 8 = (6 . 2) + 8 = 20

jawabannya D

2x+3 = y
2x = y-3
x = y-3/2

f(x) = 6(x-3/2) + 8
= 6x-18/2 + 8
= 6x-18+16/2
= 6x-2/2
= 3x-1

f(7) = 3(7)-1
= 21-1
= 20