Answer
(a.)$(fg)(x)=x^2+6x-40$.
(b.) $(fg)(-1)=-45$.
(c.)$(fg)(0)=-40$.
Work Step by Step
The given functions are
$f(x)=x-4$ and $g(x)=x+10$
(a.) $(fg)(x)=f(x)\times g(x)$
Plug both functions.
$(fg)(x)=(x-4)\times (x+10)$
Multiply the second bracket by each terms of the first bracket.
$(fg)(x)=x\times (x+10)-4\times (x+10)$
Clear the parentheses.
$(fg)(x)=x^2+10x-4x-40$
Simplify.
$(fg)(x)=x^2+6x-40$ ...... (1)
(b.) Plug $x=-1$ into function (1).
$(fg)(-1)=(-1)^2+6(-1)-40$
Clear the parentheses.
$(fg)(-1)=1-6-40$
Simplify.
$(fg)(-1)=-45$.
(c.) Plug $x=0$ into the function (1).
$(fg)(0)=(0)^2+6(0)-40$
Clear the parentheses.
$(fg)(0)=0+0-40$
Simplify.
$(fg)(0)=-40$.
