Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Determinants

Question:

If $α$ is a non-real cube root of -2, then the value of $\begin{vmatrix}1&2α&1\\α^2&1&3α^2\\2&2α&1\end{vmatrix}$, is

Options:

-11

-12

-13

0

Correct Answer:

-13

Explanation:

We have, $α = (−2)^{1/3} w$ or, $α = (− 2)^{1/3} w^2$

$∴α^3=-2$

Now, $\begin{vmatrix}1&2α&1\\α^2&1&3α^2\\2&2α&1\end{vmatrix}$

$=\begin{vmatrix}1&2α&1\\α^2&1&3α^2\\1&0&0\end{vmatrix}$  [Applying $R_3 → R_3 - R_1$]

$=6α^3-1$  [On expanding along $R_3$]

$=-13$  $[∵ α^3 = -2]$