Question

Rozwiązywanie układu równan

7. {9+4=3x
{2x+y=1

9. {7-x=3y
{x-y=9

10. {-2x-3y=12
{2x-y=20

11. {2x+2y=20
2x+3y=5

13. {2x-y=12
{-6y-5x=18

15. {2x+8y=10
{-5y-6x=16

Answer 1

{9+4=3x
{2x+y=1
---
{3x=13     |:3
{y=1-2x
---
{x=13/3
{y=1 - 2 * 13/3
---
{x=13/3
{y=3/3 - 26/3
---
{x=13/3  = 4 i 1/3
{y=-23/3  = -7 i 2/3
----------------------------------------------------------------------------------------------------
{7-x=3y
{x-y=9
--
{x=7-3y
{7-3y-y=9
--
{x=7-3y
{-4y=9-7
--
{x=7-3y
{-4y=2      |:(-4)
--
{x=7-3y
{y=-1/2
---
{x=7-3*(-1/2)
{y=-1/2
---
{x=7 + 3/2
{y=-1/2
--
{y=8 i 1/2
{y=-1/2
----------------------------------------------------------------------------------------------------
{-2x-3y=12
{2x-y=20
---
{-2x-3*(2x-20)=12
{y=2x-20
---
{-2x-6x+60=12
{y=2x-20
---
{-8x=12-60
{y=2x-20
---
{-8x=-48     |:(-8)
{y=2x-20
---
{x=6
{y=2*6-20
---
{x=6
{y=12-20
---
{x=6
{y=-8
----------------------------------------------------------------------------------------------------
{2x+2y=20    |:2
{2x+3y=5
---
{x+y=10
{2x+3y=5
---
{x=10-y
{2*(10-y)+3y=5
---
{x=10-y
{20-2y+3y=5
---
{x=10-y
{y=5-20
---
{x=10-y
{y=-15
---
{x=10-(-15)
{y=-15
---
{x=10+15
{y=-15
---
{x=25
{y=-15
----------------------------------------------------------------------------------------------------
{2x-y=12
{-6y-5x=18
---
{y=2x-12
{-6*(2x-12)-5x=18
---
{y=2x-12
{-12x+72-5x=18
---
{y=2x-12
{-17x=-54    |:-17
---
{y=2x-12
{x=54/17
---
{y=2 * 54/17 - 204/17
{x=54/17
---
{y=108/17 - 204/17
{x=54/17
---
{y=-96/17
{x=54/17
----------------------------------------------------------------------------------------------------
{2x+8y=10    |:2
{-5y-6x=16
---
{x+4y=10
{-5y-6x=16
---
{x=10-4y
{-5y-6*(10-4y)=16
---
{x=10-4y
{-5y-60+24y=16
---
{x=10-4y
{19y=16+60
---
{x=10-4y
{19y=76    |:19
---
{x=10-4y
{y=4
---
{x=10-4*4
{y=4
---
{x=10-16
{y=4
---
{x=-6
{y=4