6ax+30b^2y^2-12b^2x-15ay^2
=6ax-15ay^2+30b^2y^2-12b^2x
=3a(2x-5y^2)+6b^2(5y^2-2x)
=3a(2x-5y^2)-6b^2(2x-5y^2)
=[2x-5y^2][3a-6b^2]
=3[2x-5y^2][a-2b^2]