## Algebra 1

$a^{2}$+18a+81
In order to simplify $(a+9)^{2}$ we must apply the rule that states that $(x+y)^{2}$=$x^{2}$+2xy+$y^{2}$, and we'll set x=a and y=9. Therefore, $(a+9)^{2}$=$a^{2}$+2(a)(9)+$9^{2}$ =$a^{2}$+18a+81