已知3x^2-x=1,求6x^3=7x^2-5x+2000的值

已知3x^2-x=1,求6x^3+7x^2-5x+2000的值及过程
6x^3+7x^2-5x+2000
=x[6x^2+7x-5]+2000
=x[2x-1][3x+5]+2000
=[2x-1][3x^2+5x]+2000
=[2x-1][1+x+5x]+2000
=[2x-1][6x+1]+2000
=12x^2-4x-1+2000
=4[3x^2-x]+1999
=4*1+1999
=2003