若a²-3a+1=0,求a³+1/a³

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若a²-3a+1=0,求a³+1/a³
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若a²-3a+1=0,求a³+1/a³
若a²-3a+1=0,求a³+1/a³

若a²-3a+1=0,求a³+1/a³
a-3a+1=0 a+1=3a 等号两边同除以a得:a+1/a=3 上式等号两边同时平方得:a+1/a=7 因此:a^3+1/a^3 =(a+1/a)(a+1/a-1) =3x(7-1) =18