x的平方加2x加1减y的平方=(x+1)²-y²=(x+y+1)(x-y+1)
x²+2x+1-y²=(x+1)²-y²=(x+1+y)(x+1-y)=(x+y+1)(x-y+1)
X^2+2X+1-Y^2=(X+1)^2-Y^2=(X+Y+1)(X-Y+1)
(X2+1)2-Y 注：X外面的那个2和括号外面的2是小写的
