diketahui f(x) = 4x+5 dan g(x) = a (x-5). jika (fog)(x) = x, nilai a = ....

jawab

(fog)(x)  = x

f { g(x)}  = x
f (ax - 5a) = x
4(ax - 5a) + 5 = x
4ax - 20a + 5 = x
a(4x - 20) = x - 5
a = (x - 5)/(4x - 20)

Dik = f(x) =4x+5
g(x) = a(x-5) => ax-5a
(fog)(x)=x
Dit = a
Jb= (fog)(x)=x
4(ax-5a)+5=x
4ax-20a+5=x
4ax-20a=x-5
a(4x-20) = x-5
a= x-5/4x-20
a= 1/4