Question

Can someone clearly explain to me what i need to do and why I am doing this?

Answer 1

@Callisto @Mertsj @NotTim @phi @satellite73 @UnkleRhaukus

Answer 2

It's a matrix problem.

Answer 3

\[\left[\begin{array}{ccc}-3&6&9\\0&-3&7\\0&-1&-1 \end{array}\right]\left[\begin{array}{c}1\\1\\-7 \end{array}\right]\]
\[\sim\left[\begin{array}{ccc}-3&6&9\\0&-3&7\\(0-0)&(-3--3)&(-1-7)\end{array}\right]\left[\begin{array}{c}1\\1\\(-7-1) \end{array}\right]\qquad R_3\to R_3-R_2\]
\[\sim\left[\begin{array}{ccc}-3&6&9\\0&-3&7\\0&0&-8\end{array}\right]\left[\begin{array}{c}1\\1\\-8 \end{array}\right]\]
\[\sim\left[\begin{array}{ccc}-3&6&9\\0&-3&7\\0&0&-8/-8\end{array}\right]\left[\begin{array}{c}1\\1\\-8/-8 \end{array}\right]\qquad R_3\to R_3/-8\]
\[\sim\left[\begin{array}{ccc}-3&6&9\\0&-3&7\\0&0&1\end{array}\right]\left[\begin{array}{c}1\\1\\1 \end{array}\right]\]

Answer 4

ok so our goal is to make the second box or matrix or whatever you wanna call it, be the same?

Answer 5

and what does REF and RREF mean??

Answer 6

reduced echelon form and row reduced echelon form

echelon just means "stairs"

Answer 7

Unkles 3rd line is REF

RREF has leading 1s

Answer 8

btw that doesn't seem to be the right anwer

Answer 9

its cause @UnkleRhaukus has 7 instead of -7

Answer 10

multiply the 2nd row by -1 and add it to the 3rd row to get a new thrid row and a matrix in ref

Answer 11

the object is to get rid of that -3 in the 2nd column of the last row

Answer 12

(0 -3 -7 1) *-1

0 3 7 -1
0 -3 -1 -7
----------
0 0 6 -8 new 3rd

Answer 13

why is that the goal? we want everything under the bridge we draw to equal zero?

Answer 14

this is what i mean by bridge ^^^^