For how many values of k, is the matrix \(\left[ {\begin{array}{*{20}{c}} 0&{\rm{k}}&4\\ { - {\rm{k}}}&0&{ - 5}\\ { - {\rm{k}}}&{\rm{k}}&{ - 1} \end{array}} \right]\) singular?

This question was previously asked in
NDA (Held On: 6 Sep 2020) Maths Previous Year paper
View all NDA Papers >
  1. Only one
  2. Only two
  3. Only four
  4. Infinite

Answer (Detailed Solution Below)

Option 4 : Infinite
Free
NDA 01/2025: English Subject Test
5.7 K Users
30 Questions 120 Marks 30 Mins

Detailed Solution

Download Solution PDF

Concept:

The matrix is singular if |A| = 0

Calculations:

Given the matrix \(\left[ {\begin{array}{*{20}{c}} 0&{\rm{k}}&4\\ { - {\rm{k}}}&0&{ - 5}\\ { - {\rm{k}}}&{\rm{k}}&{ - 1} \end{array}} \right]\) singular

We know that the matrix is singular iff |A| = 0

\(\rm\begin{vmatrix} 0 &k &4 \\ -k &0 &-5 \\ -k &k &-1 \end{vmatrix} = 0\)

⇒ 0 - k (k - 5k) + 4 (- k2) = 0

⇒ 4k- 4k= 0

Therefore, we can take any value of k it makes the matrix singular.

Hence the total value of k is infinite.

Latest NDA Updates

Last updated on Jun 18, 2025

->UPSC has extended the UPSC NDA 2 Registration Date till 20th June 2025.

-> A total of 406 vacancies have been announced for NDA 2 Exam 2025.

->The NDA exam date 2025 has been announced. The written examination will be held on 14th September 2025.

-> The selection process for the NDA exam includes a Written Exam and SSB Interview.

-> Candidates who get successful selection under UPSC NDA will get a salary range between Rs. 15,600 to Rs. 39,100. 

-> Candidates must go through the NDA previous year question paper. Attempting the NDA mock test is also essential. 

More Matrices Questions

Get Free Access Now
Hot Links: master teen patti teen patti wala game teen patti rules teen patti customer care number teen patti star