Answer:
[tex] {3y}^{3} - 12y \\ = 3y( {y}^{2} - 4) \\ = 3y( {y}^{2} - {2}^{2} ) \\ = 3y(y - 2)(y + 2) \\ = 3y(y + 2)(y - 2)[/tex]
a^2-b^2=(a+b)(a-b)
a=y b=2
3y(y+2)(y-2)
