所以3x^2-x-1=0
6x³+7x²-5x+2006
=6x^3-2x^2-2x+9x^2-3x-3+2009
=2x(3x^2-x-1)+3(3x^2-x-1)+2009
=0+0+2009=2009
6x³+7x²-5x+2006=2x(3x²-x)+9x²-5x+2006=3(3x²-x)+2006=2009
3x²-x=1
6x³+7x²-5x+2006
=(6x³-2x²)+9x²-5x+2006
=2x(3x²-x)+9x²-5x+2006
=2x+9x²-5x+2006
=9x²-3x+2006
=3(3x²-x)+2006
=3+2006
=2009
6x³+7x²-5x+2006
=2x(3x^2-x)+9x^2-5x+2006
=9x^2-3x+2006
=3(3x^2-1)+2006
=3*1+2006
=2009