若3x²-x=1求6x³+7x²-5x+1994的值

6x³+7x²-5x+1994
=6x³-2x²-9x²-5x+1994
=2x(x²-x)-9x²-5x+1994
=2x-9x²-5x+1994
=-9x²-3x+1994
=-3(3x²-x)+1994
=-3x1+1994
=1994-3
=1991
再问： 额 我看的别人的 说答案是1997啊
再答： 哦，刚才写错符号了 6x³+7x²-5x+1994 =6x³-2x²+9x²-5x+1994 =2x(x²-x)+9x²-5x+1994 =2x+9x²-5x+1994 =9x²-3x+1994 =3(3x²-x)+1994 =3x1+1994 =3+1994 =1997