## College Algebra (6th Edition)

$48xy$
$$(3x+4y)^2-(3x-4y)^2$$ First square each binomial. To square a binomial, use the formula $(a+b)^2 = a^2+2ab+b^2$ and $(a-b)^2 = a^2-2ab+b^2$: $$=(3x)^2+2(3x)(4y)+(4y)^2 -[(3x)^2-2(3x)(4y)+(4y)^2]$$ $$=9x^2+24xy+16y^2-(9x^2-24xy+16y^2)$$ $$=9x^2+24xy+16y^2-9x^2+24xy-16y^2$$ $$=48xy$$