
已知x2-3x+1=0,求代数式2x3-3x2-7x+2009的值
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2x3-3x2-7x+2009
=2x(3x-1)-3x^2-7x+2009
=6x^2-2x-3x^2-7x+2009
=3x^2-9x+2009
=3(x^2-3x)+2009
=3*(-1)+2009
=2006
=2x(3x-1)-3x^2-7x+2009
=6x^2-2x-3x^2-7x+2009
=3x^2-9x+2009
=3(x^2-3x)+2009
=3*(-1)+2009
=2006
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