Ответ:

1) x= 6; y= -1/9

2) x= -1; y= 2 & x= 5; y= 8

3) x= 8/5; y= 11/5

4) x= 1; y= 2

Объяснение:

1:

2x + 3xy = -2-----------------(1)

x - 3xy = 8

-3xy = 8 - x

y = (x - 8)/3x----------------(2)

2x + 3x[(x-8)/3x)] = -2

2x - x - 8 = -2

x = 6;

y = (6 - 8)/3*6

y = -1/9

2)

xy + 3x = 5

xy = 5 - 3x --------------(1)

3y - xy = 4

3y - 5 - 3x = 4

3y - 3x = 4 + 5

y - x = 3

y = x + 3 -------(2)

(3 + x) x = 5 - 3x

x^2 + 6x = 5

x( x + 6 ) = 5

x = 5 или x = -1

если x = 5 то y = 3 + x; y = 3 + 5; y = 8

если x = -1 то y = 3 +x; y = 3 -1; y = 2

3)

x^2 - 4xy + 4y^2 = 36

(x-2y)^2 = 6^2

x = 6 - 2y-----------(1)

3y - x = 5

3y - 6 + 2y = 5

y = 11 / 5

x = 6 - 2*11/5

x = 8/5

4)

9x^2 -1 = 6xy - y^2

(3x)^2 - 2 * 3x * y + y^2 = 1

3x - y = 1

y = 3x - 1------(1)

2x + y = 4

2x + 3x - 1 = 4

5x = 5

x = 1

y = 3 * 1 - 1

y = 2