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2010-02-22T19:43:12+01:00
1.{x+y=7
x-y=1
------
2x = 8
x =4
x+y = 7
4+y=7
y=3
x=4

2.{2x -y=4
x+y=11
-------
3x= 15
x=5
x+y= 11
5+y = 11
y= 6
x=5

3.{x-2y= -3 | *(-2)
2x+3y=8

{ -2x + 4y = 6
2x+3y=8
---------
7y = 14
y= 2
2x + 3*2 = 8
2x = 2
x = 1
y = 2
2010-02-22T23:33:12+01:00
1.
{x+y=7
x-y=1

x=7-y
7-y-y=1
-2y=-6
y=3

x=7-3
x=4


2.
{2x -y=4
x+y=11

x=11-y
2(11-y)-y=4
22-2y-y=4
-3y=-18
y=6

x=11-6
x=5


3.
{x-2y= -3
2x+3y=8

x=-3+2y
2(-3+2y)+3y=8
-6+4y+3y=8
7y=14
y=2

x=-3+2*2
x=-3+4
x=1