Answer
$49x^2+70x+25-16y^2$
Work Step by Step
To find the product of the sum and difference of two terms, use the formula: $(a+b)(a-b)=a^2-b^2$. $$[(7x+5)+4y][(7x+5)-4y]=(7x+5)^2-(4y)^2$$ The square of a binomial can be found using the formula $(a+b)^2=a^2+2ab+b^2$: $$=[(7x)^2+2(7x)(5)+(5)^2]-16y^2$$ $$=49x^2+70x+25-16y^2$$
