#### Answer

$(4-7y)(4+7y)$

#### Work Step by Step

RECALL:
A difference of two square can be factored using the formula
$a^2-b^2=(a-b)(a+b)$
The given binomial can be written as:
$=4^2-(7y)^2$
The binomial above is a difference of two squares.
Factor the difference of two squares using the formula above with $a=4$ and $b=7y$ to obtain:
$=(4-7y)(4+7y)$