Question

1.

{2x - y =4

x + y = 8

2.

{x - y =3

2x +4y =0

3.

{2x- y = -6

y= 12

4.

{x= 2y

2x + 3y = 14

Proszę o jak najszybszą odpowiedź (jak by co to są układy równań, tylko nie umiem dodać tych klamerek po boku).

Answer 1

1.

 

2x-y=4    /-2x

x+y=8

 

-y=4-2x

x+y=8

 

y=-4+2x

x-4+2x=8

 

y=-4+2x

3x=12 / :3

 

x=4

y=-4+2*4

 

x=4

y=4

 

2.

 

x-y=3 / +y

2x+4y=0

 

x=3+y

2(3+y)+4y=0

 

x=3+y

6+2y+4y=0

 

x=3+y

6y=-6

 

x=3+y

y=-1

 

x=3-1

y=-1

 

x=2

y=-1

 

3.

 

2x- y = -6

y= 12

 

2x-12=-6

y=12

 

2x=6

y=12

 

x=3

y=12

 

4.

x= 2y

2x + 3y = 14

 

x=2y

2*2y+3y=14

 

x=2y

7y=14

 

x=2y

y=2

 

x=2*2

y=2

 

x=4

y=2

 

 

Answer 2

1.

2x-y = 4

x+y=8

 

2x-y = 4

x=8-y

 

2*(8-y)-y = 4

16-2y-y = 4

-3y = 4-16

-3y = -12 /:(-3)
y=4

 

x+y = 8

x+4 = 8

x=8-4

x=4

 

2.

x-y=3

2x+4y = 0

 

x-y = 3  /*(-2)

2x+4y = 0

 

-2x+2y = -6

2x+4y = 0

dodajemy stronami

 

6y = -6 /:6

y = -1

 

x+1 = 3

x = 3-1

x = 2

 

3.

2x-y = -6

y=12

 

2x-12 = -6

2x = 12-6

2x = 6 /:2

x = 3

 

y = 12

 

4.

x = 2y

2x+3y = 14

 

2*2y +3y = 14

4y+3y = 14

7y = 14 /:7

y=2

 

x = 2y

x = 2*2

x = 4