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

$49-42x^4+9x^8$
Using $(a+b)^2=a^2+2ab+b^2$ or the square of a binomial, the given expression, $\left( 7-3x^4 \right)\left( 7-3x^4 \right)$, is equivalent to \begin{array}{l}\require{cancel} \left( 7-3x^4 \right)^2 \\\\= (7)^2+2(7)(-3x^4)+(-3x^4)^2 \\\\= 49-42x^4+9x^8 .\end{array}