令y=x+1 ,则原式化成 (y-1)^2 + (1-1/y)^2 = 3 把平方展开y^2 - 2y + 1 + 1- 2/y + (1/y)^2 = 3 整理得 [y^2+2+(1/y)^2] - 2(y+1/y) = 3 ...