Mathematics 2018 Jamb Examination
Mathematics 2018 Jamb Examination
Question 61
If \( \displaystyle N = \begin{pmatrix} 3 & 5 & -4 \\ 6 & -3 & -5 \\ -2 & 2 & 1 \end{pmatrix} \), find \( \displaystyle |N| \).
Expand along the first row:
\[ \displaystyle |N| = 3 \begin{vmatrix} -3 & -5 \\ 2 & 1 \end{vmatrix} - 5 \begin{vmatrix} 6 & -5 \\ -2 & 1 \end{vmatrix} + (-4) \begin{vmatrix} 6 & -3 \\ -2 & 2 \end{vmatrix} \]
\[ \displaystyle = 3(-3 - (-10)) - 5(6 - 10) - 4(12 - 6) \]
\[ \displaystyle = 3(7) - 5(-4) - 4(6) \]
\[ \displaystyle = 21 + 20 - 24 = 17 \]
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