How do you find (fog)(x) given f(x)=-9x+3 and g(x)=x^4?

Sep 20, 2016

$\left(f o g\right) \left(x\right) = - 9 {x}^{4} + 3$

Explanation:

$\left(f o g\right) \left(x\right) \equiv f \left[g \left(x\right)\right]$

Here $f \left(x\right) = - 9 x + 3$ and $g \left(x\right) = {x}^{4}$

Hence: $f \left[g \left(x\right)\right]$ = $f \left({x}^{4}\right)$

$= - 9 {x}^{4} + 3$