what is the solution of the matrix ?

- anonymous

what is the solution of the matrix ?

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- anonymous

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- xapproachesinfinity

do you have to do it with matrices?

- anonymous

um i think soo , would you do this the same way you would do it if it was addtion ?if that makes sense

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- anonymous

addition *

- anonymous

ill show you what im talking about

- anonymous

this is what i am talking about would i do it the same but just multiply ?

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- xapproachesinfinity

not really getting your point
inverse of 2x2 matrix can be computed like this
|dw:1433291928663:dw|

- xapproachesinfinity

i see your point, you need inverse and them multiplciation operation of matrices
there is not addition here

- perl

$$\Large {A}\mathbf{ x} = \mathbf{b}
\\ \Large \mathbf{ x} = A^{-1} \mathbf{b}$$

- anonymous

I know ...... :(((((

- xapproachesinfinity

try to find the determinant first

- anonymous

now how would i find that , i usually use a online matrix calculator to find the determinant so i wouldn't know how to find on my own

- xapproachesinfinity

ok the determinant is computed like this
|dw:1433292400098:dw|

- anonymous

ok

- xapproachesinfinity

you multiply ad and bc
and then subtract

- anonymous

ok
thats all ?

- xapproachesinfinity

do the same with your matrix

- xapproachesinfinity

no not finished that's only how to do determinant

- anonymous

ok im writing this down

- xapproachesinfinity

ok

- anonymous

cross multiply ?

- xapproachesinfinity

yeah seems like cross multiply
then take the difference

- anonymous

so for me it would me 9*1 &4*2 for A and for X it would be -9*-8 and -6 *-1 right?

- anonymous

or did you mean multiply A with X ???

- xapproachesinfinity

so here
\[A=\begin{bmatrix}9&4\\ 2&1\end{bmatrix}\]
\[\det(A)=9(1)-2(4)=9-8=1\]

- xapproachesinfinity

oh no what are you taling about? are you following what i'm saying haha

- anonymous

yeah

- anonymous

9*1 i did that 2*4 i did that too

- xapproachesinfinity

we are looking for X
and i used what perl did
X=Ainverse times B

- anonymous

i know what i did wrong i forgot to subtract ..

- xapproachesinfinity

it was AX=B
then we multiplied A^-1
and we got
X=A^{-1}B
now we are in the process of computing A inverse
that is why we need determinant of A

- xapproachesinfinity

no seems you missed the whole poiint from what i understand from your last reply

- anonymous

no .. i didn't you said cross multiply then subtract right ???

- xapproachesinfinity

that's only for determinant

- xapproachesinfinity

i did that for you already see my replay above

- xapproachesinfinity

\(\color{blue}{\text{Originally Posted by}}\) @xapproachesinfinity
so here
\[A=\begin{bmatrix}9&4\\ 2&1\end{bmatrix}\]
\[\det(A)=9(1)-2(4)=9-8=1\]
\(\color{blue}{\text{End of Quote}}\)

- anonymous

ok so what do have to do next then ?

- anonymous

find x ?

- xapproachesinfinity

|dw:1433293368759:dw|

- anonymous

yup

- xapproachesinfinity

so we do 1/det A
so 1/1 =1
here we didn't need to worrt about it since it is just 1

- anonymous

ok

- xapproachesinfinity

next step is to do a switch|dw:1433293517899:dw|

- xapproachesinfinity

you take A and switch a and d
b and no switch you just change the sign

- anonymous

ok i get that but where do the negatives come from

- xapproachesinfinity

it is a rule you need to read about it on your notes

- xapproachesinfinity

what kind of class are taking

- anonymous

algebra 2

- xapproachesinfinity

hmm really?
i don't really know how much you know about matrices

- xapproachesinfinity

hmm this really needs some time to get accustomed to!
it may be fairly easy, but needs a lot of practice
you might want to look at some video tutorial on youtube

- anonymous

okay , i will

- xapproachesinfinity

once you feel comfortable then tackle problem
it is no helping to do problem you are not ready to do
be real, no matter how much i explain to you here, you will need the lecture first
here open study will not give you the lecture rather help assist you with difficulties you are having after knowing the lecture and know fairly enough on the subject

- xapproachesinfinity

i will do your problem now, but next problem you need to try your hardest :)

- anonymous

okay

- xapproachesinfinity

let me do it on paper ans take a picture

- anonymous

ok

- xapproachesinfinity

almost hehe

- anonymous

kay

- xapproachesinfinity

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- xapproachesinfinity

before the last line i preformed matrix multiplication

- xapproachesinfinity

is it readable ?

- anonymous

yeah it is . -5 ,26 -9 and -60 correct right

- xapproachesinfinity

there is no -9

- anonymous

oh ,

- xapproachesinfinity

that's just brackets

- xapproachesinfinity

that should match C

- anonymous

oh , my bad it looked like a negative for a second but yes it is C

- xapproachesinfinity

okay

- xapproachesinfinity

hope that helps

- anonymous

it does ,,,,, THANKS ..

- xapproachesinfinity

my pleasure

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