If f (x) = 3x-9 and g (x) = x^2, what is (g0f) (5)

We are asked to find z = g0f or what is the same:

z = g (f (x))

That is, we must introduce the function f (x) within the function g (x)

So, we have

f (x) = 3x-9

g (x) = x ²

Therefore we have the following function

z = (3x-9) ²

Finally (g0f) (5) = (3 (5) - 9) ²

(g0f) (5) = 36