Question

Diket = f(x) = 6x-3
g (x) = 5x+4
( fog) (a) = 81
tentukan nilai a !!!

Answer 1

Cari dulu (fog)(x)
(fog)(x) = f(g(x)) = 6(5x+4) - 3
= 30x + 24 - 3
(fog)(x) = 30x + 21

(fog)(a) = 30a + 21 = 81
30a = 60
a = 60/30 = 2

Answer 2

F(9(a)) = 81
6(5a+4)-3 = 81
30a+24-3 = 81
30a = 60 -> a = 2