#### Answer

$$(7x+8y)(7x-8y)$$

#### Work Step by Step

$49x^{2}-64y^{2}$
This is the difference between two squares.
There is a simple formula for this case:
$x^{2}-y^{2}=(x+y)(x-y)$
So, applying this formula,
We need to take the square of both terms.
$\sqrt 49x^{2}=7x$
$\sqrt 64y^{2}=8y$
So the answer would look like:
$$(7x+8y)(7x-8y)$$
(One with a positive sign and one with a negative sign.)