解：?$① $?當(dāng)?$a=1，$??$b=-3，$??$c=-1$?時(shí)，
?$x_{1}=\frac {3+\sqrt {13}}2，$??$x_{2}=\frac {3-\sqrt {13}}2$?
?$② $?當(dāng)?$a=1，$??$b=2，$??$c=1$?時(shí)，?$x_{1}=x_{2}=-1$?
?$③ $?當(dāng)?$a=1，$??$b=1，$??$c=2$?時(shí)，
此時(shí)?$b^2-4ac=-7<0，$?方程無(wú)解
