(x+3y)2+2(x2-y2)(x2+y2)+(x-3y)2.

问题描述:

(x+3y)2+2(x2-y2)(x2+y2)+(x-3y)2

原式=x2+6xy+9y2+2x4-2y4+x2-6xy+9y2=2x2+18y2+2x4-2y4