- так называемое возвратное или симметричное уравнение.
х=0 не является решением этого уравнения (2*0+0-6*0+0+2=2≠0).
Разделим обе части уравнения на х². Получим:
![2x^2+x-6+\frac{1}{x} +\frac{2}{x^2}=0 2x^2+x-6+\frac{1}{x} +\frac{2}{x^2}=0](https://tex.z-dn.net/?f=2x%5E2%2Bx-6%2B%5Cfrac%7B1%7D%7Bx%7D%20%2B%5Cfrac%7B2%7D%7Bx%5E2%7D%3D0)
Сделаем группировку следующим образом:
![2(x^2+\frac{1}{x^2})+(x+\frac{1}{x})-6=0 2(x^2+\frac{1}{x^2})+(x+\frac{1}{x})-6=0](https://tex.z-dn.net/?f=2%28x%5E2%2B%5Cfrac%7B1%7D%7Bx%5E2%7D%29%2B%28x%2B%5Cfrac%7B1%7D%7Bx%7D%29-6%3D0)
Делаем подстановку:
,
тогда
![t^2=(x+\frac{1}{x})^2\\ t^2=x^2+2*x*\frac{1}{x}+\frac{1}{x^2}\\ t^2=x^2+2+\frac{1}{x^2}\\ x^2+\frac{1}{x^2}=t^2-2 t^2=(x+\frac{1}{x})^2\\ t^2=x^2+2*x*\frac{1}{x}+\frac{1}{x^2}\\ t^2=x^2+2+\frac{1}{x^2}\\ x^2+\frac{1}{x^2}=t^2-2](https://tex.z-dn.net/?f=t%5E2%3D%28x%2B%5Cfrac%7B1%7D%7Bx%7D%29%5E2%5C%5C%20t%5E2%3Dx%5E2%2B2%2Ax%2A%5Cfrac%7B1%7D%7Bx%7D%2B%5Cfrac%7B1%7D%7Bx%5E2%7D%5C%5C%20%20t%5E2%3Dx%5E2%2B2%2B%5Cfrac%7B1%7D%7Bx%5E2%7D%5C%5C%20x%5E2%2B%5Cfrac%7B1%7D%7Bx%5E2%7D%3Dt%5E2-2)
Таким образом, уравнение примет вид:
![2(t^2-2)+t-6=0\\\\2t^2-4+t-6=0\\2t^2+t-10=0\\D=1+4*2*10=81\\t_{1} =\frac{-1+9}{4} =2\\t_{2}=\frac{-1-9}{4}=-\frac{10}{4} =-\frac{5}{2} 2(t^2-2)+t-6=0\\\\2t^2-4+t-6=0\\2t^2+t-10=0\\D=1+4*2*10=81\\t_{1} =\frac{-1+9}{4} =2\\t_{2}=\frac{-1-9}{4}=-\frac{10}{4} =-\frac{5}{2}](https://tex.z-dn.net/?f=2%28t%5E2-2%29%2Bt-6%3D0%5C%5C%5C%5C2t%5E2-4%2Bt-6%3D0%5C%5C2t%5E2%2Bt-10%3D0%5C%5CD%3D1%2B4%2A2%2A10%3D81%5C%5Ct_%7B1%7D%20%3D%5Cfrac%7B-1%2B9%7D%7B4%7D%20%3D2%5C%5Ct_%7B2%7D%3D%5Cfrac%7B-1-9%7D%7B4%7D%3D-%5Cfrac%7B10%7D%7B4%7D%20%20%3D-%5Cfrac%7B5%7D%7B2%7D)
Возвращаемся к старой переменной:
![1) x+\frac{1}{x} =2\\\\x^2-2x+1=0\\(x-1)^2=0\\x=1\\\\2)x+\frac{1}{x}=-\frac{5}{2}\\x^2+\frac{5}{2}x+1=0\\ 2x^2+5x+2=0\\D=25-4*2*2=25-16=9\\x_{1}=\frac{-5+3}{4}=-0.5\\ x_{2}=\frac{-5-3}{4}=-2 1) x+\frac{1}{x} =2\\\\x^2-2x+1=0\\(x-1)^2=0\\x=1\\\\2)x+\frac{1}{x}=-\frac{5}{2}\\x^2+\frac{5}{2}x+1=0\\ 2x^2+5x+2=0\\D=25-4*2*2=25-16=9\\x_{1}=\frac{-5+3}{4}=-0.5\\ x_{2}=\frac{-5-3}{4}=-2](https://tex.z-dn.net/?f=1%29%20x%2B%5Cfrac%7B1%7D%7Bx%7D%20%3D2%5C%5C%5C%5Cx%5E2-2x%2B1%3D0%5C%5C%28x-1%29%5E2%3D0%5C%5Cx%3D1%5C%5C%5C%5C2%29x%2B%5Cfrac%7B1%7D%7Bx%7D%3D-%5Cfrac%7B5%7D%7B2%7D%5C%5Cx%5E2%2B%5Cfrac%7B5%7D%7B2%7Dx%2B1%3D0%5C%5C%202x%5E2%2B5x%2B2%3D0%5C%5CD%3D25-4%2A2%2A2%3D25-16%3D9%5C%5Cx_%7B1%7D%3D%5Cfrac%7B-5%2B3%7D%7B4%7D%3D-0.5%5C%5C%20x_%7B2%7D%3D%5Cfrac%7B-5-3%7D%7B4%7D%3D-2)
Ответ: 1; -0,5; -2