## Introductory Algebra for College Students (7th Edition)

$81-90x+25x^2$
Using $(a\pm b)^2=a^2\pm2ab+b^2$ or the square of a binomial, the square of the given expression, $( 9-5x )^2,$ is \begin{array}{l}\require{cancel} (9)^2-2(9)(5x)+(5x)^2 \\\\= 81-90x+25x^2 .\end{array}