Home > Matrix & Vector > Solving Systems of linear equations > Solving systems of linear equations using Gauss Elimination Back Substitution method example

4. Gauss Elimination Back Substitution method example ( Enter your problem )
  1. Example `2x+5y=21,x+2y=8`
  2. Example `2x+5y=16,3x+y=11`
  3. Example `2x+3y-z=5,3x+2y+z=10,x-5y+3z=0`
  4. Example `x+y+z=3,2x-y-z=3,x-y+z=9`

3. Example `2x+3y-z=5,3x+2y+z=10,x-5y+3z=0`





Solve Equations 2x+3y-z=5,3x+2y+z=10,x-5y+3z=0 using Gauss Elimination Back Substitution method

Solution:
Total Equations are `3`

`2x+3y-z=5 -> (1)`

`3x+2y+z=10 -> (2)`

`x-5y+3z=0 -> (3)`

Converting given equations into matrix form
`2``3``-1``5`
`3``2``1``10`
`1``-5``3``0`


`R_2 larr R_2-1.5xx R_1`

 = 
`2``3``-1``5`
`0``-2.5``2.5``2.5`
`1``-5``3``0`


`R_3 larr R_3-0.5xx R_1`

 = 
`2``3``-1``5`
`0``-2.5``2.5``2.5`
`0``-6.5``3.5``-2.5`


`R_3 larr R_3-2.6xx R_2`

 = 
`2``3``-1``5`
`0``-2.5``2.5``2.5`
`0``0``-3``-9`


`i.e.`

`2x+3y-z=5 ->(1)`

`-2.5y+2.5z=2.5 ->(2)`

`-3z=-9 ->(3)`

Now use back substitution method
From (3)
`-3z=-9`

`=>z=(-9)/(-3)=3`

From (2)
`-2.5y+2.5z=2.5`

`=>-2.5y+2.5(3)=2.5`

`=>-2.5y+7.5=2.5`

`=>-2.5y=2.5-7.5=-5`

`=>y=-5xx-2/5=2`

From (1)
`2x+3y-z=5`

`=>2x+3(2)-1(3)=5`

`=>2x+3=5`

`=>2x=5-3=2`

`=>x=(2)/(2)=1`

Solution using back substitution method.
`x=1,y=2 and z=3`






This material is intended as a summary. Use your textbook for detail explanation.
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