题:已知x²-7x+2=0.求x²+1/x²的值
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![题:已知x²-7x+2=0.求x²+1/x²的值](/uploads/image/z/3134758-22-8.jpg?t=%E9%A2%98%3A%E5%B7%B2%E7%9F%A5x%26%23178%3B-7x%2B2%3D0.%E6%B1%82x%26%23178%3B%EF%BC%8B1%EF%BC%8Fx%26%23178%3B%E7%9A%84%E5%80%BC)
题:已知x²-7x+2=0.求x²+1/x²的值
题:已知x²-7x+2=0.求x²+1/x²的值
题:已知x²-7x+2=0.求x²+1/x²的值
由原方程得:x^2=7x-2 x=(7+41^1/2)/2或x=(7-41^1/2)/2 X^2+1/x^2=7x-2+1/(7x-2)代入得原式=(225+21*42^1/2)/8或原式=(225-21*41^1/2)/8