主要思路:用XX=1-3X
xx+1/xx+2x-2/x
=1-3X+1/(1-3X)+2X-2/X
=1-X+(7X+2)/(X-3XX)
=1-X+(7X-2)/(10X-3)
=(10X-3-10XX+3X+7X-2)/(10X-3)
=(20X-5-10+30X)/(10X-3)
=(50X-15)/(10X-3)
=5
已知xx+3x-1=0,求xx+1/xx+2x-2/x的值．
1个回答
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