1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值 2.已知x²+3x1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值2.已知x²+3x-1=0,求x+1/x的值
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![1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值 2.已知x²+3x1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值2.已知x²+3x-1=0,求x+1/x的值](/uploads/image/z/5597547-51-7.jpg?t=1.%E5%B7%B2%E7%9F%A5x%2B1%2Fx%3D4%2C%E6%B1%82x%26%23178%3B%2B1%2Fx%26%23178%3B%E5%92%8C%28x-1%2Fx%29%26%23178%3B%E7%9A%84%E5%80%BC+2.%E5%B7%B2%E7%9F%A5x%26%23178%3B%2B3x1.%E5%B7%B2%E7%9F%A5x%2B1%2Fx%3D4%2C%E6%B1%82x%26%23178%3B%2B1%2Fx%26%23178%3B%E5%92%8C%28x-1%2Fx%29%26%23178%3B%E7%9A%84%E5%80%BC2.%E5%B7%B2%E7%9F%A5x%26%23178%3B%2B3x-1%3D0%2C%E6%B1%82x%2B1%2Fx%E7%9A%84%E5%80%BC)
1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值 2.已知x²+3x1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值2.已知x²+3x-1=0,求x+1/x的值
1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值 2.已知x²+3x
1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值
2.已知x²+3x-1=0,求x+1/x的值
1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值 2.已知x²+3x1.已知x+1/x=4,求x²+1/x²和(x-1/x)²的值2.已知x²+3x-1=0,求x+1/x的值
1.x+1/x=4
两边平方,x²+1/x²+2=16
x²+1/x²=14
(x-1/x)²=(x+1/x)²-4=16-4=12
2.x²+3x-1=0
x²-1=3x
x-1/x=3
两边平方
x²+1/x²-2=9
x²+1/x²=11
(x+1/x)²=x²+1/x²+2=11+2=13
x+1/x=±根号13