## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$a^2-2ar+r^2$
Using $(a+b)^2=a^2+2ab+b^2$ or the square of a binomial, the given expression, $(a-r)^2 ,$ simplifies to \begin{array}{l}\require{cancel} (a)^2+2(a)(-r)+(-r)^2 \\\\= a^2-2ar+r^2 .\end{array}