Answer:
(4-7x)(4+7x)
Step-by-step explanation:
This is a difference of squares. (16 is the square of 4, 49x^2 is the square of 7x.)
The formula for difference of squares is a^2 - b^2 = (a-b)(a+b)
16 - 49^2 = (4-7x)(4+7x)
