Question

zad1

{2x+3y=9

{x-2y=1

zad2

{2x-y=10

{2x-3y=-18

zad3

{2x+y=-1

{x+2y=4

Answer 1

zad1

{2x+3y=9

{x-2y=1

 

2x+3y=9

x=1+2y

 

2(1+2y)+3y=9

x=1+2y

 

2+4y+3y=9

x=1+2y

 

7y=7           |:7

x=1+2y

 

y=1

x=1+2*1

 

y=1

x=1+2

 

y=1

x=3

 

zad2

{2x-y=10

{2x-3y=-18

 

2x-10=y

2x-3(2x-10)=-18

 

y=2x-10

2x-6x+30=-18

 

y=2x-10

-4x=-18-30

 

y=2x-10

-4x=-48        |:(-4)

 

y=2x-10

x=12

 

y=2*12-10

x=12

 

y=24-10

x=12

 

y=14

x=12

 

zad3

{2x+y=-1

{x+2y=4

 

y=-1-2x

x=4-2y

 

y=-1-2(4-2y)

x=4-2(-1-2x)

 

y=-1-8+4y

x=4+2+4x

 

y-4y=-9

x-4x=6

 

-3y=-9           |:(-3)

-3x=6            |:(-3)

 

y=3

x=-2

 

Answer 2

Zad 1

{2x+3y=9

{x-2y=1 /*[ -2]

 

{2x+3y=9

{-2x+4y = -2

 

3y +4y=9+[-2]

7y=9-2

7y=7/7

y=1

 

{y=1

{x-2y=1

 

{y=1

{x-2*1 =1

 

{y=1

{x-2 =1

 

{y=1

{x=2+1

 

{y=1

{x=3

Zad 2

 

{2x-y=10/*[-1]

{2x-3y=-18

 

{-2x +y = -10

{2x-3y = -18

 

y+[-3y] = -10 +[-18]

y-3y=-10-18

-2y=-28/ [-2]

y=14

 

{y=14

{2x-3y =-18

 

{y=14

{2x - 3*14 = -18

 

{y=14

{2x - 42 = -18

 

{y=14

{2x=42 -18

 

{y=14

{2x=24 /2

 

{y=14

{x=12

 

Zad 3

{2x+y=-1

{x+2y=4 /* [-2]

 

{2x+y = -1

{-2x -4y =-8

 

y+[-4y] = -1 +[-8]

-3y =-9 / [-3]

y = 3

 

{y=3

{x +2*3 = 4

 

 

{y=3

{x+6 =4

 

{y=3

{x=-6+4

 

{y=3

{x=-2