已知3y^2-2y+6的值为8
即3y^2-2y-2=0 y=2±√(4+24)/6=(1±√7)3
又3y^2=2y+2
代入
2/(3y^2-y+1)
=2/(2y+2-y+1)
=2/(y+3)
=6/(9+1±√7)
=6/(10±√7)
=2(10+√7)/31或2(10-√7)/31