已知a^2-3a+1=0求3/1+a²+2a²-5a-2的值.
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已知a^2-3a+1=0求3/1+a²+2a²-5a-2的值.
已知a^2-3a+1=0求3/1+a²+2a²-5a-2的值.
已知a^2-3a+1=0求3/1+a²+2a²-5a-2的值.
由a²-3a+1=0
得1+a²=3a
所以3/(1+a²)+2a²-5a-2
=3/(3a)+2(a²-3a+1)+a
=1/a+a
由a²-3a+1=0
两边同时除以a得
a-3+1/a=0
得a+1/a=3
所以3/(1+a²)+2a²-5a-2=a+1/a=3
答案:3