Question

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a) b) c) d)

{2x-2y=7 {0,4x+0,3y=1,4 {2x+3y+14 {1/2x-2y=8

{4x+3y=21 {0,1x+3y=2,3 {3x-2y=8 {2x+5y=6

Answer 1

a)

2x-2y=7 /*(-2)

4x+3y=21

 

-4x+4y=-14

4x+3y=21

 

7y=7

y=1

2x-2=7

2x=9

x=4,5

 

b)

4x+3y=14 /*(-10)

x+30y=23

 

-40x-30y=-140

x+30y=23

 

-39x=-117

x=3

3+30y=23

30y=20

y=2/3

 

c)

2x+3y=14 /*3

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

 

6x+9y=42

-6x+4y=-16

 

13y=26

y=2

6x+18=42

6x=24

x=4

 

d)

1/2x-2y=8 /*(-4)

2x+5y=6

 

-2x+8y=-32

2x+5y=6

 

13y=-26

y=-2

2x-10=6

2x=16

x=8

 

 

 

 

 

Answer 2

a) {2x-2y=7

{4x+3y=21

 

{-4x+4y=14

{4x+3y=21

___________

7y=7 /:7

y=1

2x-2·1=7

2x-2=7

2x=7+2

2x=9 /:2

{x=4,5

{y=1

b)

{0,4x+0,3y=1,4 /·(-10)

{0,1x+3y=2,3

 

{-4x-3y=-14

{0,1x+3y=2,3

_____________

-3,9x=-11,7 /:(-3,9)

x=3

-4·3-3y=-14

-12-3y=-14

-3y=-14+12

-3y=-2 /(-3)

{y=⅔

{x=3

c)

{2x+3y=14 /·2

{3x-2y=8/·3

 

{4x+6y=28

{9x-6y=24

_____________

13x=52 /:13

x=4

2·4+3y=14

8+3y=14

3y=14-8

3y=6

{y=2

{x=4

d)

{1/2x-2y=8 /·(-4)

{2x+5y=6

 

{-2x+8y=-32

{2x+5y=6

________________

13x=-26 /:13

y=-2

2x+5·(-2)=6

2x-10=6

2x=6+10

2x=16/:2

{x=8

{y=-2