因式分解3(x-y)a³+27（y-x）×a
问题描述：
因式分解3(x-y)a³+27（y-x）×a
答
3(x-y)a³+27（y-x）×a
=3(x-y)a³-27(x-y)×a
=3a(x-y)(a方-9)
=3a(x-y)(a+3)(a-3)