﹙x²＋y²﹚²－4x²y²=x^4+2x²y²+y^4-4x²y²=x^4-2x²y²+y^4=﹙x²-y²﹚²=(x+y)²(x-y)² 不懂可追问,有帮助请采纳,谢谢!...