Help me with matrices? :)

Question

aravindg · Answer

Question? :)

anonymous · Answer

attachment

aravindg · Answer

Take all the coefficients and form a 3 x 3 matrix.

anonymous · Answer

In all honesty i have no idea whats going on in my class im trying to catch up fast:/

aravindg · Answer

AX=B is the matrix equation.

A is coefficient matrix and B is constant term matrix.

aravindg · Answer

First make a matrix A using the coefficients of x,y,z

anonymous · Answer

ahhh i think i'm just gunna guess on this one I literally know nothing  :p

aravindg · Answer

Guess? You taking a test?

anonymous · Answer

It's just a small quiz type thing

aravindg · Answer

Well getting help during the test is a bad idea. Come back after it and we can do the review!

anonymous · Answer

It's a quick check so its not a test but thanks anyways! :)

anonymous · Answer

$$0x+2y+7z\
-3x-7y+0z\
7x+0y-8z$$
coefficients are 
$$0,2,7\
-3,-7,0\
7,0,-8$$

anonymous · Answer

something like
$$
  
  \left[ {\begin{array}{cccc}
   0 & 2 &-7\
   -3 & -3 &0 \
   7 & 0 &-8
  \end{array} } \right]
$$

anonymous · Answer

im not sure how you form the 3x3 matrix

anonymous · Answer

oh wait is that it?

anonymous · Answer

you need a column vector with the right hand side of the equations

anonymous · Answer

is that my answer? or does it have to be simplified more?

anonymous · Answer

that is it, but it is not done
you need the column of the answers

anonymous · Answer

-3
3
3

anonymous · Answer

not sure how to draw one here

anonymous · Answer

yeah, like that

anonymous · Answer

so is that it? thank you for helping me btw :)

anonymous · Answer

yeah, that's it
easy right?
yw

anonymous · Answer

ahhh can you help me with another :)

anonymous · Answer

sure if i can

anonymous · Answer

attachment

anonymous · Answer

to hell with matrices
this is much easier than that
multiply the first equation all the way across by $3$ and the second one all the way across by $-2$ 
you go from 
$$-3x+2y=10\
-4x+3y=2$$ to 
$$-9x+6y=30\
8x-6y=-4$$ then add them up and the $y$ terms drop out leaving you with 
$$-x=26$$ and so $x=-26$

anonymous · Answer

you good with that? you still need $y$

anonymous · Answer

Yes that was i need to figure out now.. how do i do that do i multiply?

anonymous · Answer

is it -34???

anonymous · Answer

replace $x$ by $-26$ in either equation
for example in the first one you would turn 
$$-3x+2y=10$$ so 
$$-3\times (-26)+2y=10$$ or 
$$78+2y=10$$ and that is easy to solve

anonymous · Answer

yes

anonymous · Answer

Ahh thank you so much <3 :D

anonymous · Answer

$$78+2y=10\
2y=-68\
y=-34$$ you win
yw