Use the “difference of squares” rule to factor the following expression

49-4y^2
my answer is going to be (7-2y)(7-2y)
I wasn't sure if it could of been (7-2y)(7+2y)

2 answers

Your answer should be (7-2y)(7+2y).
If you multiply the first equation (7-2y)(7-2y) it would equal 49-14y-14y+4y^2. After simplifying it would equal 49-28y+4y^2. The second option multiplies out to 49+14y-14y-4y^2. The 14y's cancel each other. That leaves 49-4y^2. Hope that helps.
Thank You So Much Sam! :)