Question

F(x) = x2 + 720 – 1
g(20) = –22 - 9
Find: (fºg)(20)

Answer 1

The tricky part is rewriting g(x + 2) as g(x) instead.

Start by substituting u = x + 2

u = x + 2

x = u - 2

Now we have:

g(u) = 3(u - 2) + 1

g(u) = 3u - 6 + 1

g(u) = 3u - 5

We have the function g with a single variable. So we could replace it back to x:

g(x) = 3x - 5

So the question becomes much simpler:

f(x) = 2x

g(x) = 3x - 5

To find f(g(x)), just put in g(x) = 3x - 5 into f(x)

f(x) = 2x

f(g(x)) = 2 * g(x)

f(g(x)) = 2(3x - 5)

f(g(x)) = 6x - 10

Answer:

6x - 10

g(x+2)=3x+1