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QUESTION

Evaluate the determinant of the matrix
$\left(\begin{array}{ccc}1&1&2\\-1&0&1\\2&1&1\end{array}\right).$




ANSWER

$\det\left(\begin{array}{ccc}1&1&2\\-1&0&1\\2&1&1\end{array}\right)=1(0-1)-1(-1-2)+2(-1-0)\\
=-1-1(-3)+2(-1)=-1+3-2=0$




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