bai  2.10
p y=-x^2/4
d y=m(x-1)-2
a. 
b. A=x1^2x2+x1x2^2 dat min
x1+x2=-4m
x2.x1=-4m-8=0

A=x1.x2(x1+x2)=(4m+8).4m
A=16m(m+2)=16.(m^2+2m)
A=16+(m+1)^2>=16
dang thuc m=-1
GTNnA=16 khi m=-1

bai 2.9
p y=-x^2/2
d y=2(x-1)

a. ve  (p cong prabol di qua goc quay xuing
, d la duong thang  qua hai diem (1;0); (0;-2)
b.
hdgd pxd
x^2 +4x-4=0
∆=4+4=8>o 
p va d khong tiep xuc cat nhau 2diem pb
=> ≠≠ dccm
c.
khong ton tai diem A