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2009-11-30T21:04:59+01:00
A)5x-y=7
2(x-1)=2y
y=5x+7
2(x-1)=2(5x+7)
2x-2=10x+14
2x-10x=14+2
-8x=16/:(-8)
-x=-2

x= 2
y=17

b) 4(x-2)-y=1
2x-4y=8
4x-8-y=1
2x-4y=8
4x-8-1=y
2x-4(4x-8-1)=8
2x-16x+32+4=8
2x-16x=8-32-4
-14x=-28

x=2
y= - 1

c) a/3 + b/5=7 / ×15
a/4- b/5=0 / × 20
5a+3b=105
5a-4b=0
5a=105-3b
105-4b-3b=0
-7b=105 / :(-7)
b= 15
5a+3×15=105
5a+45=105
5a=60

a=12
b=15

d) k/3 + l/4=1 / ×12
k/4+ l/8=1 / ×8
4k + 3l = 12
2k + l = 8
4k+3l=12
l=8-2k
4k+3(8-2k)=12
4k+24-6k=12
4k-6k=12-24
-2k=-12

k=6
l= - 4


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2009-11-30T21:08:29+01:00
A)5x-y=7
2(x-1)=2

-y=7-5x/*(-1)
2x-2=2

y=-7+5x
2x=2+2

y=-7+5x
2x=4/:2

y=-7+5x
x=2

y=-7+5*2
x=2

y=-7+10
x=2

y=3
x=2

b)4(x-2)-y=1
2x-4y=8

4x-8-y=1
2x-4y=8

4x-y=1+8
2x-4y=8

4x-y=9/*(-4)
2x-4y=8

-16x+4y=-36
2x-4y=8

-14x=-28/:(-14)
x=2

2x-4y=8
x=2

2*2-4y=8
x=2

4-4y=8
x=2

-4y=8-4
x=2

-4y=4/:(-4)
x=2

y=-1
x=2











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