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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. If Δ(a, b, c, α) = 0 for every α > 0, then which one of the following is correct ? 

  2. What are the values of x that satisfy the equation \(\left| {\begin{array}{*{20}{c}} x&0&2\\ {2x}&2&1\\ 1&1&1 \end{array}} \right| + \left| {\begin{array}{*{20}{c}} {3x}&0&2\\ {{x^2}}&2&1\\ 0&1&1 \end{array}} \right| = 0\;?\)

  3. If x + a + b + c = 0, then what is the value of \(\left| {\begin{array}{*{20}{c}} {x + a}&b&c\\ a&{x + b}&c\\ a&b&{x + c} \end{array}} \right|?\)

  4. Which one of the following factors does the expansion of the determinant

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  5. If \(u, v\) and \(w\) (all positive) are the \(p^{\text{th}}, q^{\text{th}}\) and \(r^{\text{th}}\) terms of a GP, then the determinant of the matrix is \(\begin{vmatrix} \ln u & p & 1 \\ \ln v & q & 1 \\ \ln w & r & 1 \end{vmatrix}.\)

  6. Let matrix B be the adjoint of a square matrix A, l be the identify matrix of same order as A. If k (≠ 0) is the determinate of the matrix A, then what is AB equal to?

  7. What is the determinant of the matrix?

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     | z      x      z+x |

     | y      z      x+y |    

  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

  9. Which of the following determinants have value zero?

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    3. \(\left| {\begin{array}{*{20}{c}} 0&c&b\\ { - c}&0&a\\ { - b}&{ - a}&0 \end{array}} \right|\)

    Select the correct answer using the code given below.

  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. Let $A$ and $B$ be two invertible matrices of order $3 \times 3$. If $\det(A^2 B (A^T)^3) = 16$ and $\det(A^3 B^{-2}) = 32$, then $\det(B^2 A^{-1} (B^T)^3)$ is equal to:

  2. The value of determinant \(\left| {\begin{array}{*{20}{c}} {a - b - c}&{2a}&{2a}\\ {2b}&{b - c - a}&{2b}\\ {2c}&{2c}&{c - a - b} \end{array}} \right|\) is:

  3. If \(\left| {\begin{array}{*{20}{c}} 5&a\\ a&2 \end{array}} \right| = \left| {\begin{array}{*{20}{c}} 2&1\\ 3&2 \end{array}} \right|\), then the values of a are:

  4. The value of the determinant \(\left| {\begin{array}{*{20}{c}} {\sqrt {13} + \sqrt 3 }&{2\sqrt 5 }&{\sqrt 5 }\\ {\sqrt {15} + \sqrt {26} }&5&{\sqrt {10} }\\ {3 + \sqrt {65} }&{\sqrt {15} }&5 \end{array}} \right|\) is

  5. The determinant \(\left| {\begin{array}{*{20}{c}} {xp + y}&x&y\\ {yp + z}&y&z\\ 0&{xp + y}&{yp + z} \end{array}} \right| = 0,\) if

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