Выразить одну переменную через
другую
• x+2y=7;
• Х-5y=-2;
2x+y=7;
4x+y=6;

{2(x-2y)=x-8y

{5(x+y)=2(x-y)+10

{2x-4y=x-8y

{5x+5y=2x-2y+10

{2x-4y-x+8y=0

{5x+5y-2x+2y=10

{x+4y=0|*3

{3x+7y=10

-{3x+12y=0

-{3x+7y=10

5y=10|:5

y=2

3x+12*2=0

3x=-24|:3

x=-8

{3(x+4y)-4x=2(2x+y)

{7(x-5y)+6x=3(x+4y)+27

{3x+12y-4x=4x+2y

{7x-35y+6x=3x+12y+27

{-x+12y-4x-2y=0

{13x-35y-3x-12y=27

{-5x+10y=0|*2

{10x-47y=27

+{-10x+20y=0

+{10x-47y=27

-27y=27|:(-27)

y=-1

-10x-1*20=0

-10x=20|:(-10)

x=-2

{15+2(x+3y)=3(4x+y)

{2(5x-y)-3y=2+3(2x-y)

{15+2x+6y=12x+3y

{10x-2y-3y=2+6x-3y

{2x+6y-12x-3y=-15

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

{-10x+3y=-15|*2

{4x-2y=2|*3

+{-20x+6y=-30

+{12x-6y=6

-8x=-24|:(-8)

x=3

12*3-6y=6

-6y=6-36

-6y=-30|:(-6)

y=5

{5(7x+2y)-11y=6(2x+y)+2 {33+3(6x-5y)=3(x+2y)-5y

{35x+10y-11y=12x+6y+2

{33+18x-15y=3x+6y-5y

{35x-y-12x-6y=2

{18x-15y-3x-6y+5y=-33

{23x-7y=2|*16

{15x-16y=-33|*7

-{368x-112y=32

-{105x-112y=-231

263x=263|:263

x=1

15*1-16y=-33

-16y=-33-15

-16y=-48|:(-16)

y=3

x=7-2y

(7-2y)×(-7)=-2