What is 3[f(x + 2)] if f(x) = x^3 + 2x^2 - 4?

Nov 6, 2017

I tried this:

Explanation:

You substitute your function with $x + 2$ instead of $x$ to get:

$3 \left[\textcolor{red}{{\left(x + 2\right)}^{3} + 2 {\left(x + 2\right)}^{2} - 4}\right] =$

$= 3 \left[{x}^{3} + 6 {x}^{2} + 12 x + 8 + 2 {x}^{2} + 8 x + 8 - 4\right] =$

$= 3 \left[{x}^{3} + 8 {x}^{2} + 20 x + 12\right] =$

$= 3 {x}^{3} + 24 {x}^{2} + 60 x + 36$