# System of linear equations.

• Oct 29th 2010, 03:39 PM
newgirl2012
System of linear equations.
Hi! This is my first post and hopefully someone will be able to help me! I have tried this problem atleast 10 times but I am just getting frustrated... it's not working! Here it is:

you have to solve for x, y, and z.. and I could get one but then it doesnt work for the other problems...:(

2x+y+z=4

3x-y+4z=11

x-y+5z=20
• Oct 29th 2010, 04:04 PM
Plato
If you combine the first and second you can get $5x+5z=15$.

If you combine the second and third you can get $2x-z=-9$.

Can you solve that two variable system?
• Oct 29th 2010, 04:11 PM
newgirl2012
THANKS!I got :
x=2
z+1
y=-7

Am I correct?? HOW did you do that?! I have tried and tried with no luck.. at one point I thought x=4 so maybe I just needed to divide or something.. Maybe I'm not a lost cause after all! THANKS so much!
• Oct 29th 2010, 04:16 PM
newgirl2012
Thanks!
• Oct 29th 2010, 04:23 PM
newgirl2012
I think I got it now! I got a little excited before that you made progress and I missed the (-)! NOW this is what I got:

x= -2
y=3
z= 5

? Howd I do? THANKS so much! Sorry If im posting too much I'm just so glad to have this answer! (Rofl)
• Oct 29th 2010, 04:31 PM
Wilmer
Correct. To see if you're correct, simply substitute your values
in one of the original equations; OK?
• Oct 29th 2010, 04:48 PM
newgirl2012
Thank you so much! VERY much appreciated!! If I may ask how long did it really take you to do that? I sat literally for 45 minutes trying to do it and no luck! But I did find that on my paper what Plato wrote so I need to pay more attention to the (-) and such. Thanks again!