My Math Forum matrix method for simultaneous equations

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 August 14th, 2018, 10:12 PM #1 Senior Member     Joined: Jan 2012 Posts: 745 Thanks: 7 matrix method for simultaneous equations I have used matrix method of solving simultaneous equation on these x + y + z = 5 2x - y + 3z = 16 3x + 2y - z = 3. All the results I get when substituted into the original equation does not tarry with what is on ground, until I used the old traditional method and got x = -9, y = 2, z = 12, and substituted the values to the original equations and it worked. Now my take is that you cannot use matrix method or Cramer rule to solve the equation. If I am lying, prove me wrong. Am ready to learn maybe if I missed something along the line when solving. Last edited by skipjack; August 15th, 2018 at 01:26 AM.
 August 15th, 2018, 12:19 AM #2 Senior Member   Joined: Feb 2016 From: Australia Posts: 1,822 Thanks: 643 Math Focus: Yet to find out. You might like to play around here. The solutions have working attached. Thanks from topsquark
August 15th, 2018, 12:44 AM   #3
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Quote:
 Originally Posted by Chikis I have used matrix method of solving simultaneous equation on these x + y + z = 5 2x - y + 3z = 16 3x + 2y - z = 3. All the results I get when substituted into the original equation does not tarry with what is on ground, until I used the old traditional method and got x = -9, y = 2, z = 12, and substituted the values to the original equations and it worked. Now my take is that you cannot use matrix method or Cramer rule to solve the equation. If I am lying, prove me wrong. Am ready to learn maybe if I missed something along the line when solving.
Your solution doesn't work. Is there a typo? W|A (here) and I (I verified W|A's result by Cramer's rule) get x = 35/13, y = -12/13, z = 42/13.

-Dan

Last edited by skipjack; August 15th, 2018 at 01:30 AM.

August 15th, 2018, 01:25 AM   #4
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Quote:
 Originally Posted by Chikis I used the old traditional method and got x = -9, y = 2, z = 12, and substituted the values to the original equations and it worked.
In that case, your third equation was 3x + 21y - z = 3, not 3x + 2y - z = 3.

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