a<0 ?????????2=a-b+ca+c=b+2x=0时,y=c>0,x=1时,y=a+b+c<0,b+2+b<02b<-2b<-1x1x2=c/a<0x1+x2=-b/a-2即-2<-b/a<0-b/a>-2,b>2a,a-b/a<0,b/a>0,所以应该是b<-1,a<-1/2
C>2对吧？由X1,X2坐标得-2所以A<-1
3，A,<-1
