solve the system using gaussian elimination. i need help filling in the blank

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zlanzr6

Mathematics

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Explanation & Answer

x + 2y + 3z = 11,.......................1

3x + 8y + 5z = 27.........................2

- x + y + z = 2...............................3

now

Multiply eq 1 by 3 and subtracting 2 from 1, we get

3x + 6y + 9z = 33

3x + 8y + 5z = 27
-     -       -        - 
-------------------------

- 2y + 4z = 6

- y + 2z = 3

y - 2z  = - 3 ................................4

Now multiply eq 3 by 3 and adding with eq 2, we get

3x + 8y + 5z = 27

- 3x + 3y + 3z = 2
-----------------------

  11y + 8z = 29 .........................5

Now multiplying eq 4 by 4 and adding with eq 5, we get

4y - 8z = - 12

11y + 8z = 29
------------------

15y = 17

y = 15/17

For z, put y = 15/17 in eq 4, we get

15/17 - 2z = - 3

15/17 + 3 = 2z

2z = (15 + 51) /17

2z = 66/17

z = 33/17

Now for x, put y= 15/17 and z = 33/17 in eq 3, we get

- x + 15/17 + 33/17 = 2

x = 15/17 + 33/17 - 2

L.C.M is 17, then

x = (15 + 33 - 34)/17

x = 14/17

Hence the solution is 

{x, y, z} = {14/17, 15/17, 33/17}


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