Step-by-step explanation:

1) 12(2a−3b)2−15(2a−3b)

48a2−144ab+108b2−30a+45b

=3(16a2−48ab+36b2−10a+15b)

3) 3(x−2y)2+6(2y−x)

3x2−12xy+12y2−6x+12y

=3(x2−4xy+4y2−2x+4y)

2) i don't know how to do it