Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Determinants

Question:

If $\begin{vmatrix}a&b&0\\0&a&b\\b&0&a\end{vmatrix}=0$, then

Options:

a/b is one of the cube roots of unity

a is one of the cube roots of unity

b is one of the cube roots of unity

a/b is one of the cube roots of -1

Correct Answer:

a/b is one of the cube roots of -1

Explanation:

We have,

$\begin{vmatrix}a&b&0\\0&a&b\\b&0&a\end{vmatrix}=0$

$⇒a^3+b^3=0$  [On expanding the determinant on LHS]

$⇒(a/b)^3=-1$

⇒ a/b is one of the cube roots of -1