Ejercicio 91

1.am-bm+an-bn.
2.a2x2-3bx2+a2y2-3by2.
3.x2-a2+x+a2x.
4.x+x2-xy2-y2.
5.3a-b2-2b2x-6ax.
6.6ax+3a+1+2x.
7.2x2y+2xz2+y2z2+xy3.
8.6m-9n+21nx-14mx.
9.1+a+3ab+3b.
10.4am3-12amn-m2+3n.