Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Applications of Derivatives

Question:

If $\begin{vmatrix} a+x & a-x & a-x\\a-x&a+x & a-x\\a-x&a-x&a+x\end{vmatrix}=0$ then the values of x are :

Options:

0, a

a, 2a

0, 3a

0, 2a

Correct Answer:

0, 3a

Explanation:

The correct answer is Option (3) → 0, 3a

$\begin{vmatrix} a+x & a-x & a-x\\a-x&a+x & a-x\\a-x&a-x&a+x\end{vmatrix}$

$C_1→C_1+C_2+C_3$

$\begin{vmatrix} 3a-x & a-x & a-x\\3a-x&a+x & a-x\\3a-x&a-x&a+x\end{vmatrix}$

$⇒(3a-x)\begin{vmatrix} 1 & a-x & a-x\\1&a+x & a-x\\1&a-x&a+x\end{vmatrix}$

so $R_2→R_2-R_1$, $R_3→R_3-R_1$

$(3a-x)\begin{vmatrix} 1 & a-x & a-x\\2&2x & 0\\0&0&2x\end{vmatrix}=0$

$⇒4x^2(3a-x)=0$

$⇒x=0,3a$