已知mm_5m_1=0,则2mm_5m+1/mm=?

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已知mm_5m_1=0,则2mm_5m+1/mm=?

已知mm_5m_1=0,则2mm_5m+1/mm=?
已知mm_5m_1=0,则2mm_5m+1/mm=?

已知mm_5m_1=0,则2mm_5m+1/mm=?
由m^2-5m-1=0有m-1/m=5,平方可得m^2+(1/m)^2=27,故2m^2-5m+(1/m)^2=m^2+(1/m)^2+m^2-5m=27+1=28.