## Algebra: A Combined Approach (4th Edition)

Answer: $x^{2}$ + 18x + 81
$(x + 9 )^{2}$ This will result in a perfect square trinomial, which can be generalized as $(a + b )^{2}$ = $a^{2}$ + 2ab + $b^{2}$. Here, a = x, and b = 9. Thus, $(x + 9 )^{2}$ = $x^{2}$ + 2(9)(x) + $9^{2}$ = $x^{2}$ + 18x + 81.