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2010-02-07T19:29:49+01:00
4)2x+y=2
y=0

2x+0=2
y=0

x=1
y=0

5)-2x+3y=0
x=3

-2(3)+3y=0
x=3

3y=6
x=3

y=2
x=3

6)3x-2y=4
y=1

3x-2=4
y=1

3x=6
y=1

x=2
y=1

7)3x+y=10
y=2x

x=2
y=4

8)x+2y=14
y=3x

7x=14
y=3x

x=2
y=6

9(4x-y=9
y=x

3y=9
y=x

y=3
x=3

10)3x+y=1
y=-2x

x=1
y=-2

11)4x+2y=6
y=-x

2x=6
y=-x

x=3
y=-3

14)2x-4y=18
y=5x

2x-20x=18
y=5x

x=1
y=5

15)3x+6y=12
x=-3y

3y=12
x=-3y

y=4
x=-12

16)x+y=3
x-y=1

1+y+y=3
x=1+y

y=2
x=3

17)2x+y=1
x-y=2

2(2+y)+y=1
x=2+y

y=1
x=3

18)-3x+2y=1
x-y=3

-3x+2y=1
x=3+y

-9-3y+2y=1
x=3+y

y=-8
x=-5

19)x+y=9
x-y=-1

-1+y+y=9
x=-1+y

y=5
x=4

20)x+y=8
x-y=0

y=4
x=4

21)y-x=-7
x+y=13

y-x=-7
x=13-y

y-13+y=-7
x=13-y

2y=6
x=13-y

y=3
x=10

22)2x+y=3
x+y=1

2x+y=3
x=1-y

2(1-y)+y=3
x=1-y

2-2y+y=3
x=1-y

-y=1 /-
x=2

y=-1
x=2

23)4x-y=3
x+y=7

4x-y=3
x=7-y

4(7-y)-y=3
x=7-y

28-4y-y=3
x=7-y

-5y=-25
x=7-y

y=5
x=2

24)x-5y=1
x-2y=4

x-5y=1
x=4+2y

4+2y-5y=1
x=4+2y

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

y=1
x=6

27)5x-y=21
y-2x=-3

5x-y=21
y=-3+2x

5x+3-2x=21
y=-3x+2x

3x=18
y=-3x+2

x=6
y=-16

29)2x-2y=10
x+2y=20

2x-2y=10
x=20-2y

2(20-2y)-2y=10
x=20-2y

40-4y-2y=10
x=20-2y

-6y=-30
x=20-2y

y=5
x=10

30)x=37-4y
2x+5y=53

2(37-4y)+5y=53
x=37-4y

74-8y+5y=53
x=37-4y

-3y=-21
x=37-4y

y=7
x=9