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Question

Consider the following statements in respect of the determinant Δ =

\(\Delta = \begin{vmatrix} k(k + 2) & 2k + 1 & 1 \\ 2k + 1 & k + 2 & 1 \\ 3 & 3 & 1 \end{vmatrix}\)

I. Δ is positive if k > 0.
II. Δ is negative if k < 0.
III. Δ is zero if k = 0. 
How many of the statements given above are correct? 

This question was previously asked in
NDA 2 2025 GAT Question Paper (14-Sep-2025)
The correct answer is

One

1, it's negative for 0 < k < 1 and zero at k = 1, making the statement only partially correct. Statement II is entirely correct because for all k < 0, (k - 1)³ is always negative. Statement III is incorrect since at k = 0, Δ equals (-1)³ = -1 ≠ 0. Therefore, only Statement II is completely correct out of the three given statements. The answer is that exactly one statement is correct.

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Similar Questions

  1. How many matrices of different orders are possible with elements comprising all prime numbers less than 30?

  2. If (a - b) (b - c) (c - a) = 2 and abc = 6, then what is the value of \(\begin{vmatrix}a & b & c \\ a^2 & b^2 & c^2 \\ a^3 & b^3 & c^3 \end{vmatrix}?\)

  3. Under which of the following conditions does the determinant \(\begin{vmatrix}a & b & c \\ b & c & a \\ c & a & b\end{vmatrix}\)  vanish?

    1. a + b + c = 0

    2. a 3+ b 3+ c 3= 3abc

    3. a 2+ b 2+ c 2- ab - bc - ca = 0

    Select the correct answer using the code given below:

  4. If \(ABC\) is a triangle, then what is the value of the determinant
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  5. If \(a, b, c\) are the sides of triangle \(ABC\), then what is
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  6. If in a triangle ABC, sin3A + sin3B + sin3C = 3sinAsinBsinc, then what is the value of the determinant \(\begin{vmatrix}a & b & c \\b & c & a \\c & a & b\end{vmatrix}\) where a,b,c are sides of the triangle?

  7. For what value of $n$ is the determinant
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  8. If B is a non-singular matrix and A is a square matrix, then the value of det (B -1 AB) is equal to

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  10. If A is an invertible matrix of order n and k is any positive real number, then the value of [det(kA)] -1 det A is


Important Questions from Determinants

  1. An $n \times n$ square matrix $A$ satisfies $A^T = A^{-1}$. The determinant of this matrix may take which of the following value(s)?
  2. The determinant of the matrix $\begin{pmatrix} 1 & p & q + r \\ 1 & q & r + p \\ 1 & r & p + q \end{pmatrix}$ is ______.

  3. Let $f(x) = \begin{vmatrix} x^3 & \sin x & \cos x \\ 6 & -1 & 0 \\ p & p^2 & p^3 \end{vmatrix}$ 

    where $p$ is a constant. 

    The value of $\frac{d^3}{dx^3}f(x)$ at $x = 0$ is

  4. How many matrices of different orders are possible with elements comprising all prime numbers less than 30?

  5. If A is a square matrix of order 3 and det A = 5, then what is det [(2A) -1 ] equal to ?

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