The domain for f(x) and g(x) is the set of all real numbers.


Let f(x) = x2 + 1 and g(x) = 3x.


Find f · g.


A.
x2 + 3x + 1


B.
3x3 + 3x


C.
3x3 + 3x + 1


D.
x2 + 3x