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

$x^4-2x^2y^2+y^4$
Using $(a\pm b)^2=a^2\pm2ab+b^2$ or the square of a binomial, the square of the given expression, $(x^2-y^2)^2 ,$ is \begin{array}{l}\require{cancel} (x^2)^2-2(x^2)(y^2)+(y^2)^2 \\\\= x^4-2x^2y^2+y^4 .\end{array}