# Thread: Help with rref function

1. ## Help with rref function

I have a Ti30x and my instructor is telling me that I need to perform this problem using the rref function, which the Ti30x doesnt have. I have to show a ck for my solution also. Can anybody help?

10x+6y+z=7
5x-9y-2z=3
15x-12y+2z=-5

Todd

2. Originally Posted by Firefightinfool
I have a Ti30x and my instructor is telling me that I need to perform this problem using the rref function, which the Ti30x doesnt have. I have to show a ck for my solution also. Can anybody help?

10x+6y+z=7
5x-9y-2z=3
15x-12y+2z=-5
Is this what you have? I doubt it can do matrices at all, given the single-line output. You will probably have to row-reduce by hand, but this particular problem should be fairly easy (it's only a 3x3, after all).

3. Yes, its the Ti30IIS.

4. Im asking if you could complete it for me?

5. Originally Posted by Firefightinfool
10x+6y+z=7
5x-9y-2z=3
15x-12y+2z=-5
My 89 gives

$\displaystyle \left[\begin{matrix} 1&0&0&3/5\\ 0&1&0&2/3\\ 0&0&1&-3 \end{matrix}\right].$

6. Originally Posted by Firefightinfool
I have a Ti30x and my instructor is telling me that I need to perform this problem using the rref function, which the Ti30x doesnt have. I have to show a ck for my solution also. Can anybody help?

10x+6y+z=7
5x-9y-2z=3
15x-12y+2z=-5

Todd
Hi Firefightinfool,

I don't know about the TI30x, but on a TI-84+, you simply enter the matrix into your calculator, say Matrix A. I assume you can do that. You'll use the coefficients and the constant like

$\displaystyle \left(\begin {array}{cccc}10 & 6 & 1 & 7 \\ 5 & -9 & -2 & 3 \\ 15 & -12 & 2 & -5 \\ \end {array}\right)$

Then find your rref( ) (Reduced Row Echelon Form).

On a TI-84 its under matrix math.

You should get $\displaystyle \left\{\frac{3}{5}, \frac{2}{3}, -3\right\}$

If THIS is what the face of your calculator looks like, I don't see a way to enter a matrix array. Just not familiar with this model.

7. what is the syntax for entering that matrix in the TI-89 when using rref()?

(ie.. [x,y,z],[x1,y1,z1])

8. Originally Posted by zepto-
what is the syntax for entering that matrix in the TI-89 when using rref()?

(ie.. [x,y,z],[x1,y1,z1])
If you have the system of equations:

$\displaystyle \begin{array}{rcl}x+2y&=&3 \\ 4x+5y&=& 6\end{array}$

then you find the command rref( at MATH(=2ND 5) MATRIX rref( or you choose the command rref( with the catalog.

I've attached screenshots where you can find the command and how you type in the coefficients.