<span>so to factor the trinomal:
z^2+18z+81
In this problem 9*9=81 and 9+9=18, so insert 9 as the right hand term of one factor and 9 as the right-hand term of the other factor.
(z+9)(z+9)
Combine the two common factors of (z+9) by adding the exponents.
(z+9)^2</span>
