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 Question from Shawn, a student: Please help me put matrix in row echelon form: 1 9 8 0 5 8 1 35 1 -4 -1 17

Hi Shaun,

I can help get you started. I would multiply the first row by -5 and add it to the second row and then multiply the first row by -1 and add it to the third row. That gives me

$$\left( \begin{array}{rrrr}1 & 9 & 8 & 0\\ 0 & -37 & a & b\\0 & -13 & c & d\end{array} \right)$$

for some numbers $a, b, c, \mbox{ and }d.$ This looks quite ugly and might make you think that you will have to resort to fractions, but don't give up yet. Multiply the third row by -3 and add it to the second row. What do you get?

Penny

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