
Algebra PreAlgebra and Basic Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
November 19th, 2011, 07:31 PM  #1 
Senior Member Joined: Nov 2011 Posts: 101 Thanks: 0  system of equations (find x,y,z) questions
Hi. I have problem with these two questions. 1. 3x+2yz=2 4x5y+2z=1 7x+y2z=3 So I did use 1st and 2nd equation to get 10xy=3 and 1st and 3rd to get x+3y=1. If I use these two equations I get y=7/31 and when I plug this in I get x=10/31. Now I plug those two for x and y on 1st equation I get z=18/31. So solution set for this equation comes out (7/31,10/31,18/31) for x,y,z order. When I plug these 3 #s for x,y,z for 1st and 2nd equations I get 2 and 1 which is correct answer. The problem is when I plug them in 3rd equation, I don't get 3 but I get 3.64.... is my answer wrong or did I make some mistake? plz help. Here is 2nd problem I am having trouble with. I'm supposed to find x, y, z and z is arbitrary # 2. 5xy+3z=7 2x+4y+9z=11 So if z is arbitrary, I solve for y, I get y=(39z/22)+(69/22). If I plug that in y section, I get x=(21z/22)(17/22). So my answer set is ( (21z/22)(17/22), (39z/22)+(69/22), z(arbitrary) ). Is this right answer? I need help. 
November 19th, 2011, 07:56 PM  #2  
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 10,891 Thanks: 716  Re: system of equations (find x,y,z) questions Quote:
Did you not notice a shortcut: adding equations 2 and 3 right away?  
November 19th, 2011, 08:04 PM  #3  
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 10,891 Thanks: 716  Re: system of equations (find x,y,z) questions Quote:
 
November 19th, 2011, 08:18 PM  #4 
Senior Member Joined: Nov 2011 Posts: 101 Thanks: 0  Re: system of equations (find x,y,z) questions
Ok. thx. I got first one's correct answer ( (10/29), (13/29), (2/29) ) I get correct answer with these x,y,z #s. As for second one, are you sure I am right? These #s just don't look pretty enough to me to be an answer. I remember my instructor saying, I won't get pretty # answers like I did in algebra 1, 2 since this is college algebra but even so, it looks ugly. 
November 20th, 2011, 12:06 AM  #5 
Global Moderator Joined: Dec 2006 Posts: 18,142 Thanks: 1417 
The answers for the second problem may be inelegant, but they are correct.


Tags 
equations, find, questions, system 
Search tags for this page 
Click on a term to search for related topics.

Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
The system of equations (64 equations 12 unknown) solution  ZeusTheMunja  Linear Algebra  20  January 25th, 2013 06:52 AM 
System of equations?  wyckedjester  Algebra  4  October 22nd, 2012 05:31 AM 
questions the system of linear equations for problem solving  nilam sari  Linear Algebra  2  June 2nd, 2012 11:34 PM 
system of equations on NT  Pell's fish  Number Theory  1  March 26th, 2012 06:18 AM 
System of equations  proglote  Algebra  8  April 26th, 2011 07:59 PM 