## Elementary Algebra

$36a^2-12ab+b^2$
Using $(a+b)^2=a^2+2ab+b^2$, or the square of a binomial, the given expression, $(6a-b)^2 ,$ is equivalent to \begin{array}{l}\require{cancel} (6a)^2+2(6a)(-b)+(-b)^2 \\\\= 36a^2-12ab+b^2 .\end{array}