What is the probability that the roots of the equation x2 + x + n = 0 are real, where n ∈ ℕ and n < 4?

This question was previously asked in
NDA 02/2021: Maths Previous Year paper (Held On 14 Nov 2021)
View all NDA Papers >
  1. 0
  2. \(\rm \frac{1}{4}\)
  3. \(\rm \frac{1}{3}\)
  4. \(\rm \frac{1}{2}\)

Answer (Detailed Solution Below)

Option 1 : 0
Free
UPSC NDA 01/2025 General Ability Full (GAT) Full Mock Test
6 K Users
150 Questions 600 Marks 150 Mins

Detailed Solution

Download Solution PDF

Concept:

Consider the quadratic equation ax2 + bx + c = 0

Discriminant (D): D = b2 - 4ac

For real root: D ≥ 0

b2 - 4ac ≥ 0

Calculation:

Given equation 

x2 + x + n = 0

Finding discriminant: (1)2 - 4n ≥ 0

1  ≥  4n

≤ \(\rm \frac{1}{4}\)

There is no value which belongs in 1, 2, 3, ..... (i.e. natural number)

This is possible for n = 0

∴ The probability of the required event is zero.

Latest NDA Updates

Last updated on Jul 8, 2025

->UPSC NDA Application Correction Window is open from 7th July to 9th July 2025.

->UPSC had 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 Probability of Random Experiments Questions

More Probability Questions

Get Free Access Now
Hot Links: teen patti stars dhani teen patti teen patti gold apk teen patti circle teen patti wink