Question

oblicz metodą przeciwnych współczynników :

a) x+y=9

x-y=3

b)2x-11y=73

3x-4y=47

c) -2x+5y= -10

7x-4y=8

d)4x+5y=-4

6x+7y= -6

e) x+4y=11

2x+5y=10

f) 3x+2y=5

2x+2y=2

Answer 1

a) x+y=9
+ x-y=3

0=12

 

b)2x-11y=73 /*3
3x-4y=47 /*2
6x-33y=  219

-   6x-8y =94

-33y+8y= 125

-25y= 125 / *(-25)

y= 5

 

c) -2x+5y= -10 /*4
7x-4y=8 / *5

-8x+20y= -40

+  35x- 20y= 40

35x=0

 

d)4x+5y=-4 /*7
6x+7y= -6 /*5

28x+35y=-28

- 30x+35y= -30

-2x= 2

x = 1

 

e) x+4y=11 /*2
2x+5y=10
2x+8y=22

-  2x+5y=10

3y= 12 / :3

y = 4

 

f) 3x+2y=5
-   2x+2y=2
x=3

2y = 5- 3*3

2y= -4

y= -2

Answer 2

a) x+y=9

x-y=3

__________

2x=12//:2

x=6

 

x=6                                       x=6

y=9-6                                    y=3

 

b)2x-11y=73/ 3               6x-33y=219

3x-4y=47/(-2)              -6x+8y=-94

_____________

-25y=125//:(-25)

y=-5

 

y=-5                                 y=-5                           y=-5               y=-5

-6x+ 8*(-5)=-94                -6x=-94+40               -6x=-54            x=9

 

 

c) -2x+5y= -10/ 7             -14x+35y=-70

7x-4y=8 / 2                      14x-8y=16

______________

27y=-54

y=-2

 

y=-2                                y=-2                              y=-2

14x=16-16                       14x=0//:14                    x=0

 

 

 

d)4x+5y=-4/6                    24x+30y=-24

6x+7y= -6/-4                  -24x-28y=24

_______________

2y=0//:2

y=0

 

y=0                                 y=0

24x=-24//24                  x=-1

 

 

dalej już mi sie nie chce robić