# Math Help - simultaneous equations arrgh

1. ## simultaneous equations arrgh

could someone go through the steps for me for giving x,y,z in terms of m,my method is really long and wrong.

4x+y+7z=12
3x+2y+5z=m
8x+5y+13z=0

thnx alot

2. Hello,

You can use matrices..

$\begin{pmatrix} 4 & 1 & 7 \\ 3 & 2 & 5 \\ 8 & 5 & 13 \end{pmatrix} \begin{pmatrix} x \\ y \\ z \end{pmatrix}=\begin{pmatrix} 12 \\ m \\ 0 \end{pmatrix}$

And act on the first matrix (3x3)

Otherwise... it's the same method as above :

(3)-2(1) will annulate x. --> expression in terms of y and z.

(2)-2(1) will annulate y. --> expression in terms of x and z (and m).

5(1)-7(2) will annulate z. --> expression in terms of x and y (and m).

etc