已知,m²-5m-1=0,求2m²-5m+1/m²的值.
已知,m²-5m-1=0,求2m²-5m+1/m²的值.
数学人气:913 ℃时间:2020-04-08 22:19:31
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显然,m不为0,否则条件不成立.∵m^2-5m-1=0, ∴2m^2-10m=2, ∴2m^2-5m=2+5m.∵m^2-5m-1=0, ∴1-5/m-1/m^2=0, ∴1/m^2=1-5/m.∵m^2-5m-1=0, ∴m-5-1/m=0, ∴m-1/m=5, ∴5m-5/m=25.于...
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