How do you find [g of h](x) if g(x)=8-2xg(x)=82x and h(x)=3xh(x)=3x?

1 Answer
Aug 21, 2015

[ g of h ](x) = 8-6x(x)=86x

Explanation:

[g of h](x)(x) can be written as g(h(x))g(h(x))

Given g(color(blue)(x)) = 8 - 2color(blue)(x)g(x)=82x
but the xx is just a variable place holder and we can replace it with anything we like.

So g(color(blue)(w)) = 8 - 2color(blue)(w)g(w)=82w
would have identical meanings
as would
g(color(blue)(h(x))) = 8 -2 color(blue)(h(x)g(h(x))=82h(x)

Using this last form and replacing color(blue)(h(x)) on the right side with its definition: color(blue)(h(x)) = color(blue)(3x)h(x)=3x

We have
g(h(x)) = 8 - 2(color(blue)(3x))g(h(x))=82(3x)

color(white)("XXXX")= 8 - 6xXXXX=86x