Question

rozwiaz uklad rownan , stosujac odpowiednie podstawienie np w punkcie a/ podstawienie : x+y = u i x-y=t

2 ( x + y ) - 3 ( x -y ) = - 7
-5 ( x+y ) - 4 ( x-y ) = - 17

Answer 1

 2u - 3t = -7

-5u - 4t = -17

 

2u - 3t = -7 /:u

4t - 5u = -17 /:t

 

podzielić

2 - 3t

4 - 5u

 

 

Answer 2

 

2 ( x + y ) - 3 ( x -y ) = - 7
-5 ( x+y ) - 4 ( x-y ) = - 17

 

2u - 3t = -7 /*5

-5u - 4t = -17 /*2

 

10u - 15t = -35

-10u - 8t = -34

__________________

10u - 10u - 15t - 8t = -35 - 34

-23t = -69 /:(-23)

t = 3

 

2u - 3 * 3 = -7

2u - 9 = -7

2u = 2 /:2

u = 1

 

x + y = 1

x - y = 3

 

x = 1 - y

1 - y - y = 3

 

x = 1 - y

-2y = 2 /:(-2)

 

x = 1 - y

y = -1

 

x = 1 - (-1)

y = -1

 

x = 2

y = -1