已知3x^2-x-1=0,求6x^3+7x^2-5x+1999

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已知3x^2-x-1=0,求6x^3+7x^2-5x+1999

已知3x^2-x-1=0,求6x^3+7x^2-5x+1999
已知3x^2-x-1=0,求6x^3+7x^2-5x+1999

已知3x^2-x-1=0,求6x^3+7x^2-5x+1999
6x^3+7x^2-5x+1999
=x(2*3x^2+7x^2-5)+1999
=x(2*3x^2-2x-5+9x)+1999
=x[2(3x^2-x-1)+9x-3]+1999
=9x^2-3x+1999
=3(3x^2-x-1)+2002
=2002