Question

c)2x+5y=9 D)-7x-3y=10

-3x+4y=-2 5x+4y=-9

e)2x+y=14 f)3x+5y=31

5x+4y=17 x+2y=12

g)x+2y=5 h)2x-2y=4

2x-5y=-17 2x+3y=18

Answer 1

c)2

   1

e)12

   8

g)3

  14

d)20

  0

f)33

  10

h)4

  13

nie wiem czy dobrze

Answer 2

c)2x+5y=9 /*3

 -3x+4y=-2 /*2

 

6x + 15y = 27

-6x + 8y = -4

________________

6x - 6x + 15y + 8y = 27 - 4

23y = 23 /:23

y = 1

 

2x + 5 = 9

2x = 9 - 5

2x = 4 /:2

x = 2

 

D)-7x-3y=10 / *4

  5x+4y=-9 /*3

 

-28x - 12y = 40

15x + 12y = -27

__________________

15x - 28x + 12y - 12y = 40 - 27

-13x = 13 /:(-13)

x = -1

 

-7 * -1 - 3y = 10

7 - 3y = 10

-3y = 10 - 7

-3y = 3 /:(-3)

y = -1

 

e)2x+y=14 /*(-4) 

5x+4y=17

 

-8x - 4y = -56

5x + 4y = 17

_________________

5x - 8x + 4y - 4y = 17 - 56

-3x = -39 /:(-3)

x = 13

 

2 * 13 + y = 14

26 + y = 14

y = 14 - 26

y = -12

 

f)3x+5y=31

    x+2y=12 / *(-3)

 

3x + 5y = 31

-3x - 6y = -36

__________________

3x - 3x + 5y - 6y = 31 - 36

-y = -5

y = 5

 

3x + 5 * 5 = 31

3x + 25 = 31

3x = 31 - 25

3x = 6 /:3

x = 2

 

 3 * 2 + 5y = 31

6 + 5y = 31

5y = 31 - 6

5y = 25 /:5

y = 5

 

g)x+2y=5   /*(-2)

2x-5y=-17

 

-2x - 4y = -10

2x - 5y = -17

__________________

2x - 2x - 4y - 5y = -10 - 17

-9y = - 27 /:(-9)

y = 3

 

x + 2 * 3 = 5

x + 6 = 5

x = 5 - 6

x = -1

 

 h)2x-2y=4 /*(-1)

    2x+3y=18

 

-2x + 2y = -4

2x + 3y = 18

_________________

2x - 2x + 2y + 3y = 18 - 4

5y = 14 /:5

y = 14/5

y = 2,8

 

2x - 2 * 2,8 = 4

2x - 5,6 = 4

2x = 4 + 5,6

2x = 9,6 /:2

x = 4,8