## Algebra 1: Common Core (15th Edition)

$4\pi x^{2}+20\pi x+24\pi$
$S.A.=2\pi r^{2}+2\pi rh$ ...surface area of a cylinder. $=2\pi(x+2)^{2}+2\pi(x+2)(x+4)$ ...substitute $x+2$ for $r$and $x+4$ for $h$. $=2\pi(x+2)(x+2)+2\pi(x+2)(x+4)$ ...write $(x+2)^{2}$ as $(x+2)(x+2)$. $=2\pi(x^{2}+2x+2x+4)+2\pi(x^{2}+4x+2x+8)$ ...multiply binomials. $=2\pi(x^{2}+4x+4)+2\pi(x^{2}+6x+8)$ ...factor out $2\pi$. $=2\pi(x^{2}+4x+4+x^{2}+6x+8)$ ...combine like terms. $=2\pi(2x^{2}+10x+12)$ ...write in standard form. $=4\pi x^{2}+20\pi x+24\pi$