Question

Rozwiąż układy równan : 5x-2y=4

x+y=5

2x+4y=5y-1

y+5=0

Answer 1

5x-2y=4

x+y=5

 

x=5-y

5(5-y)-2y=4

 

x=5-y

25-5y-2y=4

 

x=5-y

-7y=-21

 

x=5-y

y=3

 

x=2

y=3

 

 

 

2x+4y=5y-1

y+5=0

 

y=-5

2x+4*(-5)=5*(-5) -1

 

y=-5

2x - 20= -25-1

 

y=-5

2x=-6

 

y=-5

x=-3

 

 

 

Answer 2

1.

5x-2y=4

x+y=5

 

5x-2y = 4

x = 5-y

 

5(5-y)-2y = 4

x = 5-y

 

25-5y-2y = 4

x = 5-y

 

-5y-2y = 4-25

x = 5-y

 

-7y = -21 /:-7

x = 5-y

 

y = 3

x = 5-3

 

y = 3

x = 2 

 

Spr.

5x-2y=4

x+y=5

 

5·2-2·3 = 4

2+3 = 5

 

10-6 = 4

5 = 5

 

4 = 4

5 = 5     OK.

 

                                                                      

2.

2x+4y=5y-1

y+5=0

 

2x+4y-5y = -1

y = -5

 

2x-y = -1

y = -5

 

2x-(-5) = -1

y = -5

 

2x+5 = -1

y = -5

 

2x = -1-5

y = -5

 

2x = -6 /:2

y = -5

 

x = -3

y = -5

 

Spr.

2x+4y=5y-1

y+5=0

 

2·(-3)+4·(-5) = 5·(-5)-1

-5+5 = 0

 

-6-20 = -25-1

0 = 0

 

-26 = -26

0 = 0       OK.