把(X-Y)和(X+Y)各看作一个字母因式,合并同类项3（X+Y)²-（X-Y)+2(X+Y)²+（X-Y)-5(X-Y)²=2在后面是²,2在前面是与后面相乘.

把(X-Y)和(X+Y)各看作一个字母因式,合并同类项3（X+Y)²-（X-Y)+2(X+Y)²+（X-Y)-5(X-Y)²=2在后面是²,2在前面是与后面相乘.
把(X-Y)和(X+Y)各看作一个字母因式,合并同类项3（X+Y)²-（X-Y)+2(X+Y)²+（X-Y)-5(X-Y)²=
2在后面是²,2在前面是与后面相乘.

把(X-Y)和(X+Y)各看作一个字母因式,合并同类项3（X+Y)²-（X-Y)+2(X+Y)²+（X-Y)-5(X-Y)²=2在后面是²,2在前面是与后面相乘.
5（X+Y)²-5(X-Y)²