Question

Rozwiąż układy równań metodą przeciwnych współczynników

potrzebuje na jutro!
daję 25 pkt.

z góry dziekuje

zadanie tutaj :
http://i50.tinypic.com/paixy.jpg

Answer 1

A)
3x+2y=13
2x+y=11 |i -2

3x+2y=13
-4x-2y=-22 +
_____________
x=9
2*9+y=11

x=9
y=11-18

x=9
y= - 7

b)
5x+3y=0
-x-2y=7 |*5

5x+3y=0
-5x-10y=35 +
_________________
-7y=35
y= -5

-x-2*-5=7
y= -5

-x+10=7
y= -5

x= 3
y= -5

c)

3u+2v=2 |*-2
5u+4v=6

-6u-4v=-4
5u+4v=6 +
____________
-u=2
u= - 2

3*-2+2v=2
u= - 2

-6+2v=2
u= - 2

v=4
u= - 2

d)

3s+5t= -6
1.5s-2t=-3 |*-2

3s+5t= -6
-3s+4t= 6 +
____________
9t=0
t=0

3s+5*0= -6
t=0

s= -2
t=0

e)
5=3x-y
5x-2y=7

3x-y=5 |*-2
5x-2y=7

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

3*3-y=5
x=3

9-y=5
x=3

y= 4
x=3

f)

x-3y=5 |*-3
y+3x= -5

-3x+9y= -15
3x+y= -5 +
________________
10y= -20
y= -2

x-3*-2=5
y= -2

x+6=5
y= -2

x= -1
y= -2

Tylko nie zapomnij o klamerkach :) pls p. xD

Answer 2

A)
3x+2y=13
2x+y=11 / *(-2)

3x+2y=13
-4x -2y=-22
--------------
-x= -9 / *(-1)
x=9

x=9
3 *9 +2y=13

x=9
2y= 13 -27

x=9
2y= -14 / :2

x=9
y= -7

b) 5x + 3y=0
-x -2y =7 / *5

5x+3y=0
-5x-10y=35
------------
-7y=35/: (-7)
y=-5

5x+3*(-5)=0
y=-5

5x=15/:5
y=-5

x=3
y=-5

c)
3u+2v=2 / *(-2)
5u+4v=6

-6u-4v=-4
5u+4v=6
-----------
-u=2 / *(-1)
u=-2

u=-2
5*(-2)+4v=6

u=-2
4v=6+10

u=-2
4v= 16/:4

u=-2
v=4

d)
3s+5t=-6
1,5s-2t=-3 / * (-2)

3s+5t=-6
-3s+4t=6
-------------
9t=0/:9
t=0

3s+5*0=-6
t=0

3s=-6/:3
t=0

s=-2
t=0

e)
5=3x-y
5x-2y=7

3x-y=5 / *(-2)
5x-2y=7

-6x+2y=-10
5x-2y=7
-----------
-x=-3 / * (-1)
x=3

x=3
5*3-2y=7

x=3
-2y=7-15

x=3
-2y=-8 / (-2)

x=3
y=4

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

x-3y=5
3x+y=-5 /*3

x-3y=5
6x+3y=-15
------------
7x=10 /:7
x= 1 i 3/7

x=1 i 3/7
6* 1 i 3/7 +3y= -15

x= 1 i 3/7
3y= -15 -8 i 4/7

x= 1 i 3/7
3y= -23 i 4/7 /:3

x=1 i 3/7
y= 2 i 18/21