How do i simplify 4y to the second - ( 3 - y to the second)

4y^2 - (3-y)^2 =

4y^2 - (9 -6y + y^2 ) = 4y^2 - 9 + 6y -y^2 =

3y^2 + 6y - 9 = (3y + 9)(y - 1)

I hope this helps. Thanks for asking.