Question

(fog)(x). F(x)=3x, g(x)=x+7

Answer 1

For this case we have the following functions:

$f (x) = 3x\\g (x) = x + 7$

We must find $(f_ {0} g) (x)$. By definition we have to:

$(f_ {0} g) (x) = f (g (x))$

So:

$f (g (x)) = 3 (x + 7) = 3x + 3 * 7 = 3x + 21$

Finally, the composite function is:

$(f_ {0} g) (x) = 3x + 21$

Answer:

$(f_ {0} g) (x) = 3x + 21$