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2010-02-02T18:19:33+01:00
A)
5=3x-y
5x-2y=7

3x-y=5 /×(-2)
5x-2y=7

-6x+2y=-10
5x-2y=7
----------
x=-3

-6×(-3)+2y=-10
2y=-10-18 /:2
y=-14

b)
x-3y=5
y+3x=-5

x-3y=5
3x+y=-5 /×3

x-3y=5
9x+3y=-15
------------
10x=-10 /:10
x=-1

-1-3y=5
-3y=6 /:(-3)
y=-2
2 3 2
2010-02-02T18:26:19+01:00
5 = 3x-y
+y
4 = 3x
:3
3 = 1x
--
4



5x-2y = 7
+2y
5x = 9
:5
1x = 5
----
9


x-3y= 5
+3y
1x = 8


y+3x = 5
+y
3x = 6
:3
1x =2
2010-02-02T20:20:53+01:00