Question

If `f(x) = x +5` and `g(x) = 2x + 4`, then what is `(g * f)(2)`?

Answer 1

`(g*f)(2)=56`

Explanation:

`"note "(g*f)(x)=g(x)xxf(x)`

`color(white)(xxxxxxxxxx)=(2x+4)(x+5)`

`"expand factors using the FOIL method"`

`rArr(g*f)(x)=2x^2+14x+20`

`"to obtain "(g*f)(2)" substitute x = 2 into "(g*f)(x)`

`rArr(g*f)(2)=2xx2^2+(14xx2)+20`

`color(white)(xxxxxxxxx)=8+28+20=56`