Question

The solutions of the equation $\left| \begin{matrix} x & 2 & - 1 \ 2 & 5 & x \

• 1 & 2 & x \end{matrix} \right| = 0$ are.

• A. $3, - 1$
• B. $- 3,1$
• C. 3, 1
• D. $- 3, - 1$

Answer 1

Answer: (A)

$3, - 1$

Answer 2

$\left| \begin{matrix} x & 2 & - 1 \ 2 & 5 & x \

• 1 & 2 & x \end{matrix} \right| = 0$⇒$x(5x - 2x) - 2(2x + x) - 1(4 + 5) = 0$

⇒ $3x^{2} - 6x - 9 = 0,x^{2} - 2x - 3 = 0$,$(x + 1)(x - 3) = 0$

$\Rightarrow x = - 1,3$.