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hiepgia0493

j ki za. hs bac 3 co CT thi luon la 2 CT. chu sao cau tren hoi co cuc tri, cau duoi lai noi co 2 CT nua!!
hs co CT<=>y'(x)=0 phai co 2 nghiem phan biet.
<=>g(x) = x2-2mx+m+2=0 phai co 2 nghiem phan biet
<=>delta= m2 - m - 2> 0
<=>m<-1 hoac m>2 (1)

khi do, goi hoanh do cac diem CT la x1, x2.
theo gia thiet x2>x1>0
suy ra: g(0)>0 va (x1+x2)/2 >0
suy ra: m> -2 va m>0 (2)

tu 1 va 2 suy ra m>2.
 
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