Bài 9:Ghpt
x y
1 a) 2 3
2x y 11
28
7
y 11 2x
b)
3x y 4
+ =
=
Trang 2o 2
o
2 o
o
Bài10 (21) Ghpt
x y 5
Theo viet x, y là n pt :
xy 4
t 5t 4 0
a b c 0 t 1; t 4 Hpt có n : (x 1, y 4); (x 4, y 1)
x y 1 x ( y) 1 b)
Theo viet x, y là n pt : t t 6 0
t 2; t 3 Hpt có n : (x 2, y 3); (x 3, y 2)
+ =
a)
Trang 3+ + =
=
=
=
⇔ − ⇔
= −
2 2
2 2 2
2
B i11(21) à
x y xy 5
(1)
§ Æt x y a;xy b x y 2xy a
Pt (1)
a 3 3
b 2
a
5
a 5
b 5 a
b 10
Trang 4 − =
− + = ⇔ − = ⇔ − = −
− = − = =
=
=
⇔
Bµi12 :Ghpt
2x y 3 4x 4xy y 9 (2x y) 9
2x y 3
x 3y 5 2x y 3 6x 3y 9 7x 14
x 3y 5 x 3y 5 x 3y 5
2x y 3 6x 3y 9 7x 4
x 3y 5 x 3y 5 x 3y 5
x 2
y
= −
=
1 4 x
7 13 y
7
Trang 5 − + = − − + + − =
+ = + =
− − − + − =
⇔
+ =
− − − + − = − − + =
− =
+ =
⇔
− + =
+ =
2
2 2
2 2
2 2
Bµi13 : Ghpt
6x 3xy x 1 y 6x 3xy x y 1 0
1)
x y 1 x y 1
(6x 2x) (3xy y) (3x 1) 0
x y 1
2x(3x 1) y(3x 1) (3x 1) 0 (3x 1)(2x y 1) 0
x y 1 x y 1
3x 1 0
x y 1
2x y 1 0
x y 1
=
=
⇔ + = ⇔ =
= + = +
+ =
+ + =
=
= ± = ±
=
=
= + = +
+ + = + = =
−
=
2
2 2
2 2
2 2
1
3
8 y
x y 1
9
y 2x 1 y 2x 1
x y 1 x (2x 1) 1 1
x
3
8 2 2 y
9 3
x 0
y 1
y 2x 1 y 2x 1 4
x
x (2x 1) 1 5x 4x 0 5
3 y
5
Trang 6 + + − = + = −
Bµi14.Ghpt
8
3
Trang 72
2 2 2
0
Bài15 :Ghpt
(2x y)(x 1) 0
5
3
5
Pt có n là : x 1; y
3
Trang 82 2
2
2
Bài16 :Ghpt
3(x y)(x y) 3(x y) 0
3(x y)(x y 1) 0
y
4
±
⇔ =
+
0
= ⇔ = −
+ = − ⇔ =