xx - x - 1 = 0
答案:3 悬赏:20 手机版
解决时间 2021-05-10 13:45
- 提问者网友：兔牙战士
- 2021-05-09 16:42
xx - x - 1 = 0
最佳答案
- 五星知识达人网友：迷人又混蛋
- 2021-05-09 16:48
原方程等价于：
X^2 - 2*(1/2)*X + (1/2)^2 - (1/2)^2 - 1 = 0
=> (X - 1/2)^2 - 5/4 = 0
=> (X - 1/2)^2 = 5/4
=> X - 1/2 = ±√(5/4)
=> X1 = √(5/4) + 1/2
X2 = -√(5/4) + 1/2
=> X1 = (1+√5)/2
=> X2 = (1-√5)/2
X^2 - 2*(1/2)*X + (1/2)^2 - (1/2)^2 - 1 = 0
=> (X - 1/2)^2 - 5/4 = 0
=> (X - 1/2)^2 = 5/4
=> X - 1/2 = ±√(5/4)
=> X1 = √(5/4) + 1/2
X2 = -√(5/4) + 1/2
=> X1 = (1+√5)/2
=> X2 = (1-√5)/2
全部回答
- 1楼网友：七十二街
- 2021-05-09 18:01
楼主您好，请问题目是不是x²-x-1=0呢
如果是的话，利用万能公式可以得出x=（1±√5 ）/2
- 2楼网友：思契十里
- 2021-05-09 17:16
x^2-x+0.25-5/4=0 (x-1/2)^2-5/4=0 (x-1/2+√ 5/2)(x-1/2-√ 5/2)=0 x1=1/2+√ 5/2 x2=√ 5/2-1/2
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