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3 and 4 .Determinants and Matrices
easy
The roots of the equation $\left| {\,\begin{array}{*{20}{c}}x&0&8\\4&1&3\\2&0&x\end{array}\,} \right| = 0$ are equal to
A
$( - 4,\,4)$
B
$(2,\, - 4)$
C
$(2,\,4)$
D
$(2,\,8)$
Solution
(a) We have $\left| {\,\begin{array}{*{20}{c}}x&0&8\\4&1&3\\2&0&x\end{array}\,} \right|\, = 0$
$\therefore $ $\Delta = x(x – 0) – 0(4x – 6) + 8(0 – 2)$
or ${x^2} – 16 = 0$ $ \Rightarrow $ $x = 4,\, – 4$.
Standard 12
Mathematics