Question

If f(x)=6 and g(x)=4x+1, find (fog)(x)

Answer 1

The definition

$f(x)=6$

means that f always outputs 6, no matter the input. So, if you want to compute the composition

$(f\circ g)(x)$

It means that you want to compute f giving as input the result of g(x):

$(f\circ g)(x) = f(g(x))$

But no matter the input: $f(\cdot)$ is always 6! So, we have

$(f\circ g)(x) = f(g(x)) = 6$

for every possible x.