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2009-12-20T19:26:46+01:00
A).{3s+5t=-6
1,5s-2t=-3 /*-2
{3s+5t=-6
-3s+4t=6
---------------
9t=0/:9
t=0
{3s+5t=-6/*2
1,5s-2t=-3/*5
{6s+10t=-12
7.5s-10t=-15
----------------
13,5s=-27/:13,5
s=-2
b){5=3x-y
5x-2y=7
{-3x+y=-5/*5
5x-2y=7/*3
{-15x+5y=-25
15x-6y=21
-------------------
-y=-4/:-1
y=4

{-3x+y=-5/*2
5x-2y=7
{-6x+2y=-10
5x-2y=7
--------------
-x=3/:-1
x=-3
c)
{x-3y=5
y+3x=-5
{x-3y=5/*-3
3x+y=-5
{-3x+9y=-15
3x+y=-5
-----------
10y=-20/:10
y=-2

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

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