Question

If f (x) = -3x +4 and g (x)= x squared, find (g*f) (-2)

Answer 1

The easiest way to do this is to work out f(-2) first, =-3(-2)+4=10, then find g(-2)=(-2)²=4.
(g*f)(-2)=4×10=40.
However, if g*f means g of f the answer is different, because having worked out that f(-2)=10 we put this result into g, so we find g(10)=10²=100.
So you need to determine whether g*f means g(x)×f(x) [answer 40] or g(f(x)) [answer 100] when x=-2.