If
f(x)=x^2
and
g(x)=2x+1
, and
(fg)(x)=f(x)g(x)
, what is the value of
(fg)(-2)
?

Correct answer: -12

Here,
(fg)(x)
denotes the product of the two functions:
(fg)(x)=f(x)g(x)=x^2(2x+1)
. Thus,
(fg)(-2)=(-2)^2[2(-2)+1]=4(-3)=-12
. Option C is only the value of
g(-2)
, whereas the question asks for the product of
f(-2)
and
g(-2)
. Exam tip: distinguish
(fg)
, which means product, from
f\circ g
, which means composition.