4 497X Y↓ + =↓↓↓↓A) GI I H PHẢ Ệ ƯƠNG TRỠNH SAU
1.
4
4
97
x
y
↓
+
=
↓↓↓
↓
a)
Gi i h ph
ả ệ
ươ
ng trỡnh sau:
3
3
78
x y
y x
↓↓↓
(I)
Ta cú:
x
4
+
y
4
=
(
x
2
+
y
2 2
)
-
2
x y
2 2
↓↓
+
-
=
2
2 2
2 2
x
y
x y
(
)
2
97
(1)
↓ ↓
↓↓
(I)
2
2
xy x
y
(
)
78
(2)
↓↓↓
Đ t
ặ
x2
+ y2
= u xy; = tT PT (2) suy ra ĐK:
ừ
0; 0u t
↓
-
=
↓
↓
+ -
=
( 2 )
97
u
t
2
97
↓
↓
↓
�
�
�
�
�
�
↓↓
=
�
�
�
�
↓↓
-
= -
0,5
ut
u
t
78
( 2 )
12168