3x²-x-1=0两边同除以3,得x²-(1/3)x-(1/3)=0移项,得x²-(1/3)x=(1/3)两边都加上(1/6)²,得x²-(1/3)x+(1/6)²=(1/3)+(1/6)²[x-(1/6)]²=(13/36)两边开平方,得x-(1/6)=(±√13)/6x...