IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII[r]
Trang 11
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII TÀI LIỆU LUYỆN THI ĐẠI HỌC GVBM : ĐOÀN NGỌC DŨNG
a)
) 2 ( y y x
x
) 1 ( xy 3 x y
x
3 2 2
3
2
Ta thấy x = y = 0 là một nghiệm của hệ
Xét x 0 và y 0
x 3 xy x y x 3 y x y 4 x x y 9 y 0 y
y
x
x
xy 3 x
y
3
x
3 2
2
3
2
y x
y x 1 y
x 0 9 y
x 5 y
x 4 0 y 9 y
x
2 2
2 2
2
2 4
2 2
4
2
1 y
2
1
; 2 1
4
4
2 3
3
y x xy y x y xy 4 ) 2 ( y x 4 y
x
4
) 1 ( 1 xy y
x
4 xy y x3 y3 xy2 x4 y4 3 xy3 4 x2y2 x3y 0 xy y2 4 xy x2 0
x xy
4
y
0
xy
3
x y
x y 0 y
1 x 1 y
0 x
Khi
3
x
3 3 3
25
1 y 25
3 x 25
27 x 1 x 27
25 1 9
x 27
x
3 3
25
1
; 25 3