Question

If `f(x)=4x+1` and `g(x)=x^2-5`, what is `(f*g)(4)`?

Answer 1

`(f*g)(4)=187`

Explanation:

As `f(x)=4x+1` and `g(x)=x^2-5`, substituting `x` with `g(x)` in `f(x)`, we get

`(f*g)(x)=(4x+1)(x^2-5)=4x xx x^2-4x xx5+x^2-5`

= `4x^3+x^2-20x-5`

Hence `(f*g)(4)=4xx4^3+4^2-20xx4-5`

= `4xx64+16-80-5`

= `256+16-80-5=187`