Answer
$(7y-8x)(7y+8x)$
Work Step by Step
RECALL:
A difference of two squares can be factored using the formula:
$a^2-b^2=(a-b)(a+b)$
Using the formula above, we obtain:
$49y^2-64x^2
\\= (7y)^2-(8x)^2
\\ = (7y-8x)(7y+8x)$