View Full Version : 4x4 System of Equations
sydboe
Mar 21, 2009, 10:28 AM
need work please!
x+2y+2z-w=0
x-y+3w=7
2x-y+z+w=6
2x+2y+3z-3w=-1
Curlyben
Mar 21, 2009, 10:54 AM
Thank you for taking the time to copy your homework to AMHD.
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galactus
Mar 21, 2009, 12:02 PM
I would solve this using elimination via Gaussian elimination.
Turn it into a matrix and reduce it using reduced row echelon form.
\begin{bmatrix}1&2&1&-1&0\\1&-1&3&0&7\\2&-1&1&1&6\\2&2&3&-3&-1\end{bmatrix}
When you get it into this form, you have your solutions:
\begin{bmatrix}1&0&0&0&x\\0&1&0&0&y\\0&0&1&0&z\\0&0&0&1&w\end{bmatrix}
Your solutions are in the right most column.
sydboe
Mar 22, 2009, 07:16 PM
I'm totally stuck. I've been trying to cancel out things and just wind up cancelling out the whole equation, unable to find what any letters equal
galactus
Mar 23, 2009, 10:40 AM
This is tedious stuff. In my opinion, these should be done with a calculator.
I am sorry, but I am not going to post all this step by step.
Here is a screen capture from my TI-92. Now, at least, you can see what you're shooting for.
tranced
Apr 7, 2010, 11:09 PM
the answer is
x = 16
y = 9
z =-17
w = 0 and the row manipulation is as follows
r2-r1
r3-r4
r4-2r1
r2-2r4
r3+3r2
r4+2r2
r3/-2
r4+r3
r1-2r2
r1-2r3
r1-r4
r3+2r4
tranced
Apr 7, 2010, 11:10 PM
By the way I used gauss jordan
ebaines
Apr 8, 2010, 10:36 AM
btw i used gauss jordan
Let's just hope the OP hasn't been waiting around for over a year to turn in his homework!