lim（x→∞）(x-1/x+1)^2x = lim（x→∞）(1 - 2/(x+1))^2x这是1^∞型的重要极限原式 = exp{lim（x→∞）(-2/(x+1))*(2x)} = exp{lim（x→∞）(-4x/(x + 1))} = e^(-4)
