①4（3a+2b）²-9（3a-2b）²
=[2(3a+2b)+3(3a-2b)][2(3a+2b)-3(3a-2b)]
=(15a-2b)(-3a+10b)
=-(15a-2b)(3a-10b)
②5y（x-2y）-20y（2x-y）²
=5y(x-2y)[1-4(x-2y)]
=5y(x-2y)(1-4x+8y)