Question

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D ) { 3s + 5t = - 6

1,5 s - 2t = 3

E ) { 5 = 3x - y

5x -2y= 7

F ) { x -3y =5

y + 3x = -5

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Answer 1

d)

3s+5t=-6

1,5s-2t=3 |*-2

 

3s+5t=-6

-3s+4t=-6 - sumujemy

 

0s+9t=-12

t=-4/3

s=(-6+20/3)*3=-18+20=2

 

E )

3x - y = 5 |*-2

5x -2y= 7

 

-6x +2y = -10

5x - 2y = 7

 

-x = -3

x=3

15-2y=7

y=4

 

F )

x -3y =5

y + 3x = -5

 

x - 3y = 5|*-3

3x + y = -5

 

-3x +9y = -15

3x + y= -5

10y=-20

y=-2

x=-1

Answer 2

3s + 5t = - 6                                       1,5 s - 2t = 3

1,5 s - 2t = 3 / * (-2)                           t=2,6666666

3s+5t=-6                                            1,5s-2,66666=3

-3s+4t=-6                                            1,5s=6,66666666 / : 1,5

3s-3s+4t+5t=-6+(-6)                              s= 4 i cztery dziewiąte

9t=-12 / :9                                           t=1 i jedna trzecia

t=1 i jedna trzecia

 

 

5 = 3x - y                                       5 = 3x - y

5x -2y= 7                                       x=3

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

5x -2y= 7                                        5=9-y

-6x+2y=-10                                     5-9=-y

5x -2y= 7                                        -4=-y

-6x+5x+2y-2y=-10+7                        y=4

-x=-3                                              x=3

x=3

 

 

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

y + 3x = -5                                            y=-2

-3x+9y=-15                                            -2+3x=-5

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

-3x+3x+9y+y=-5+(-15)                             x=-1

10y=-20                                                  y=-2

y=-2