4x^2-y^2x^2表示平方如有疑问，请追问；如已解决，请采纳
原式=(2x-(y-1))(2x+(y-1))=(2x)²-(y-1)²=4x²-(y²-2y+1)=4x²-y²+2y-1
(2x-y+1)(2x+y-1)=[2x-(y-1)][2x+(y-1)]=4X2-(y-1)2=4X2-y2+2y-1
