If log (x + 2) + log (x − 2) = log 5 then the value of x will be

  1. -3
  2. 3
  3. ± 3
  4. None of the above

Answer (Detailed Solution Below)

Option 2 : 3
Free
UPSC CDS 01/2025 General Knowledge Full Mock Test
120 Qs. 100 Marks 120 Mins

Detailed Solution

Download Solution PDF

Concept:

Logarithm properties

Product rule: The log of a product equals the sum of two logs.

Quotient rule: The log of a quotient equals the difference of two logs.

Calculation:

Given:

log (x + 2) + log (x − 2) = log 5

⇒ log [(x + 2) (x – 2)] = log 5                (∵ )

⇒ log (x 2 – 4) = log 5

⇒ x2 – 4 = 5

⇒ x2 = 9

∴ x = ± 3

Here x ≠ -3 is not possible because (x – 2) should be greater than zero.

∴ x = 3

Latest CDS Updates

Last updated on Jul 7, 2025

-> The UPSC CDS Exam Date 2025 has been released which will be conducted on 14th September 2025.

-> Candidates can now edit and submit theirt application form again from 7th to 9th July 2025.

-> The selection process includes Written Examination, SSB Interview, Document Verification, and Medical Examination.  

-> Attempt UPSC CDS Free Mock Test to boost your score.

-> Refer to the CDS Previous Year Papers to enhance your preparation. 

Hot Links: teen patti wala game lucky teen patti teen patti mastar