a的三次方（3a-2）+（2-3a）b的平方
=a³(3a-2)-b²(3a-2)
=(3a-2)(a³-b²)
a的二次方（3a-2）+（2-3a）b的平方
=a²(3a-2)-b²(3a-2)
=(3a-2)(a²-b²)
=(3a-2)(a+b)(a-b)