2= = +2 2 23 3 2⇒ − + + + + + = +X X X X X X X X X X ( 1 2)...
2. 2= = +2 2 23 3 2⇒ − + + + + + = +x x x x x x x x x x
(
1
2
)
3
1 2
(
1
2
) (
1
2
) (
1
2
)
+ =0x x⇒ − + =1
2
2
2
1x x x x1
1 2
2
Lại có:
MN ⊥d ⇒(
x2
−x1
)
.1+(
y2
−y1
)
.2=0⇒ − − − + + =7 2 0x x x x x x x x(
2
1
) (
2
1
) (
1
2
1 2
2
2
)
7⇒ + + =2- Xét
x1
+x2
=01
7;2
7⇒ = ± =∓2 2 − + = + =1 92
2
2
2
x x x x x x 1
1 2
2
1
2
- Xét
vô nghiệm
⇔ ⇒7 5 4 + + = x x x x x x =2 4 1 2