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Question

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jim_thompson5910 · Answer

are you able to find the inverse matrix?

jim_thompson5910 · Answer

ok glad you figured it out

anonymous · Answer

could you help me with this other one though I think I got it but I'm not sure

jim_thompson5910 · Answer

one sec

jim_thompson5910 · Answer

that is not correct since it should be a 9x2 matrix

jim_thompson5910 · Answer

what did you get when you replaced all of the letters with their numerical equivalents?

jim_thompson5910 · Answer

so you should have this 2x9 matrix (sorry there was an earlier typo where I said 9x2, I meant 2x9)

$$\Large
\begin{bmatrix}
    15  &  14  &   5  &   0   & 17 &   21   &  5  &  19  &  20\
     9  &  15  &  14  &   0  &  20  &  15 &    0    & 7  &  15
\end{bmatrix}
$$

jim_thompson5910 · Answer

you would then multiply that 2x2 matrix by the matrix I just posted

jim_thompson5910 · Answer

so you need to compute

$$\Large
\begin{bmatrix}
1 & -2\
-3 & 7 
\end{bmatrix}

\begin{bmatrix}
    15  &  14  &   5  &   0   & 17 &   21   &  5  &  19  &  20\
     9  &  15  &  14  &   0  &  20  &  15 &    0    & 7  &  15
\end{bmatrix}
$$

jim_thompson5910 · Answer

first do you know how big the answer matrix will be?

jim_thompson5910 · Answer

what's the size of the left matrix?

jim_thompson5910 · Answer

how about the right?

jim_thompson5910 · Answer

good

jim_thompson5910 · Answer

let's call the left matrix A and the right matrix B

jim_thompson5910 · Answer

matrix AB (A times B) is only defined if the number of columns in A matches with the number of rows in B

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