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Evaluate \(\left| {\begin{array}{*{20}{c}} 2&4 \\ { - 5}&{ - 1} \end{array}} \right|\)

Answer

\(18\)
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Solution

\(\left| {\begin{array}{*{20}{c}} 2&4 \\ { - 5}&{ - 1} \end{array}} \right| \)
On expansion
\(= 2(-1) - 4(-5) = -2 + 20 = 18\)
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