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Find the last number in the given sequence $\begin{pmatrix} 4& 9& 20\\ 8& 5& 14\\ 10& 3& ?\end{pmatrix}$

(It's $3\times3$ matrix)

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    @Asaf I see. Quite crafty.2012-11-19

2 Answers 2

6

The answer is $11$ since then $3 r_2 -r_1=2 r_3$ where $r_1, r_2, r_3$ are the three rows.

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    $11$ is the likely intended answer: another route using the columns would be $c_1+4c_2 = 2c_3$ as in my matrix multiplication.2012-11-19
3

One possibility is

$\begin{pmatrix} 4& 9\\ 8& 5\\ 10& 3\end{pmatrix} \begin{pmatrix} 1& 0& \tfrac12\\ 0& 1& 2\end{pmatrix}$

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    It produces the first two terms in the third column of the problem and so is a possible solution to the question. There are more.2012-11-19