7y(x-3y)²-2(3y-x)³
=7y(x-3y)²+2(x-3y)³
=(x-3y)²[7y+2(x-3y)]
=(x-3y)²(2x+y)
=1²×6
=6后面三次方是怎么拆的提取公因式（x-3y)²,另一个因式是7y+2(x-3y)