Toán 10- chuyên đề hàm số - 2b

Toán 10- chuyên đề hàm số - 2b

x(x y 1) 3 0 (1)

(x,y )

5(x y) 1 0 (2)

x

3

x y 1

x2

3(2; )

x – 2y – 1 = 0 (do x + y 0 x 1 và y 0)

x = 2y + 1

(2y 1) 2y y 2y 2(y 1)2y(y 1) 2(y 1) 2y 2 (do y + 1> 0 y 0)

(*)

1 1,

4 4

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2(a) (b)

3

5x y 4xy 3y 2(x y) 0xy(x y ) 2 (x y)

= HD

y2 – (4x + 8)y – 5x2 + 16x + 16 = 0

2 y 5x 4' 9x

5

2 2

12x 2xy y

2

y xy 5x 2

(x y) xy

42

u v

4

(3)(4)2

5

v u4

v4

x y

23xy2

4, v =

12

32

x 1 y(y x) 4y (1)(x 1)(y x 2) y (2)

= HD

0, chia hai 2

2

x 1 y x 4y

x 1 y x 2 1y

6(a) xy x 1 7y2 2 2 (b)

x y xy 1 13y

2 2

x y 3x 4y 13x 2y 9x 8y 37

x y xy 3

x 1 y 1 4

.