用换元法解题x /(x2+2)+(x2+2)/ x= -10/3x /(x²+2)+(x²+2)/ x= -10/3

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用换元法解题x /(x2+2)+(x2+2)/ x= -10/3x /(x²+2)+(x²+2)/ x= -10/3
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用换元法解题x /(x2+2)+(x2+2)/ x= -10/3x /(x²+2)+(x²+2)/ x= -10/3
用换元法解题x /(x2+2)+(x2+2)/ x= -10/3
x /(x²+2)+(x²+2)/ x= -10/3

用换元法解题x /(x2+2)+(x2+2)/ x= -10/3x /(x²+2)+(x²+2)/ x= -10/3
设x /(x²+2)=t
则原方程可化为:t+1/t=-10/3
方程两边同乘以3t得:3t²+3=-10
即:(t+3)(3t+1)=0
解得:t=-3或-1/3
1° 当t=-3时,即x /(x²+2)=-3
化简得:3x²+x+6=0
戴尔他=1-4*3*6=-71

设:x/(x²+2)=y,则:
y+(1/y)=-10/3
3y²+10y+3=0
(3y+1)(y+3)=0
则:y=-1/3或y=-3
(1)若y=-1/3,则:
x/(x²+2)=-1/3
x²+3x+2=0
(x+1)(x+2)=0
则:x=-1或x=-2

(...

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设:x/(x²+2)=y,则:
y+(1/y)=-10/3
3y²+10y+3=0
(3y+1)(y+3)=0
则:y=-1/3或y=-3
(1)若y=-1/3,则:
x/(x²+2)=-1/3
x²+3x+2=0
(x+1)(x+2)=0
则:x=-1或x=-2

(2)若y=-3,则:
x/(x²+2)=-3
3x²-x+6=0
这个方程的判别式小于0,无解。

综合,原方程的解是:x=-1或x=-2

收起

令a=x/(x²+2)
a+1/a=-10/3
3a²+10a+3=0
(3a+1)((a+3)=0
x/(x²+2)=-1/3
x²+3x+2=(x+1)(x+2)=0
x/(x²+2)=-3
3x²+x+6=0
无解
所以x=-1,x=-2