Answer
$25x^2+70xy+49y^2-4$
Work Step by Step
The given expression can be written as
$[(5x+7y)-2][(5x+7y)+2].$
The expression above is of the form $(a-b)(a+b)$.
RECALL:
(1) $(a-b)(a+b) = a^2-b^2$
(2) $(a+b)^2=a^2+2ab+b^2$
Multiply the expression using formula (1) above with $a=5x+7y$ and $b=2$ to obtain:
$=(5x+7y)^2 - 2^2
\\=(5x+7y)^2-4$
Square the binomial using formula (2) with $a=5x$ and $b=7y$ above to obtain:
$=(5x)^2+2(5x)(7y)+(7y)^2-4
\\=25x^2+70xy+49y^2-4$
