已知a^2+3a+1=0求代数式3a^3+(a^2 - 知识问答

已知a^2+3a+1=0求代数式3a^3+(a^2+5)(a^2-1)-5(a+1)(a-1)-6a的值

1个回答

3a^3+(a^2+5)(a^2-1)-5(a+1)(a-1)-6a
=a^4+3a^3-a^2-6a
=a^4+3a^3+a^2-2a^2-6a
=a^2(a^2+3a+1)-2a^2-6a
=-2a^2-6a
=-2a^2-6a-2+2
=-2(a^2+3a+1)+2
=2

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