Question

Rozwiąż układ równań metodą podstawiania .

niżej załącznik .

Answer 1

a)

{x-2y=3

{4x-3y=2

 

{x=2y+3

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

 

{x=2y+3

{8y+12-3y=2

 

{x=2y+3

{5y=2-12

 

{x=2y+3

{5y=-10   /;5

 

{y=-2

{x=2·(-2)+3=-4+3=-1

 

{x=-1

{y=-2

 

b)3x+2y=-7   /:2

{-2x+3y=9

 

{1,5x+y=-3,5

{-2x+3y=9

 

{y=-3,5-1,5x

{-2x+3(-3,5-1,5x)=9

 

{y=-3,5-1,5x

{-2x-10,5-4,5x=9

 

{y=-3,5-1,5x

{-6,5x=9+10,5

 

{y=-3,5-1,5x

{-6,5x=19,5    /:(-6,5)

 

{x=-3

{y=-3,5-1,5·(-3)=-3,5+4,5 =1

 

{x=-3

{y=1

 

 

 

 

 

 

 

 

Answer 2

a)

x-2y = 3

4x-3y = 2

 

x = 3+2y

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

 

x = 3+2y

12+8y-3y = 2

 

x = 3+2y

8y-3y = 2-12

 

x = 3+2y

5y = -10 /÷5

 

x = 3+2y

y = -2

 

x = 3+2·(-2)

y = -2

 

x = 3-4

y = -2

 

x = -1

y = -2

 

b)

3x+2y = -7

-2x+3y = 9

 

3x = -7-2y /÷3

-2x+3y = 9

 

x = (-7-2y)/3

-2( (-7-2y)/3)+3y = 9

 

x = (-7-2y)/3

(14+4y)/3+3y = 9 /·3

 

x = (-7-2y)/3

14+4y+9y = 27

 

x = (-7-2y)/3

4y+9y = 27-14

 

x = (-7-2y)/3

13y = 13 /÷13

 

x = (-7-2y)/3

y = 1

 

3x+2y = -7

y = 1

 

3x+2·1 = -7

y = 1

 

3x+2 = -7

y = 1

 

3x = -7-2

y = 1

 

3x = -9 /÷3

y = 1

 

x = -3

y = 1