Answer
3(7y-4)(y+4)
Work Step by Step
Given the polynomial
$21y^{2}$ + 72y - 48
We see that the three terms have a common factor of 3 so we factor out a 3.
3($7y^{2}$ + 24y - 16)
*** We break of the middle term into two factors that add to give +24 and multiply to give -112. The two numbers are +28 and -4.
3($7y^{2}$ + 28y - 4y - 16)
We take the GCD of the first two and the GCD of the last two terms.
3(7y(y+4)-4(y+4))
We take (y+4) and factor it out which gives us.
3(7y-4)(y+4)
