Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • NCERT
  • The first term of a G.P. is 1. The sum of the third term and fifth term is 90. Find the common ratio of G.P.

9.  The first term of a G.P. is 1. The sum of the third term and fifth term is 90. Find the common ratio of G.P.

Answers (1)

best_answer

Given: The first term of a G.P. is 1. The sum of the third term and fifth term is 90.

a=1

a_3=a.r^2=r^2                                      a_5=a.r^4=r^4

\therefore \, \, r^2+r^4=90

\therefore \, \, r^4+r^2-90=0

\Rightarrow \, \, r^2=\frac{-1\pm \sqrt{1+360}}{2}

       r^2=\frac{-1\pm \sqrt{361}}{2}

      r^2=-10 \, or \, 9

r=\pm 3

Thus, the common ratio of GP is \pm 3.

Posted by

seema garhwal

View full answer

Crack CUET with india's "Best Teachers"

  • HD Video Lectures
  • Unlimited Mock Tests
  • Faculty Support
cuet_ads

Similar Questions

Trending Articles/News

anam-khan

CBSE Date Sheet 2025 (Out) Live: Class 10, 12 board exam time table at cbse.gov.in; syllabus, sample papers
anam-khan

CBSE Class 12 board exam date sheet 2025 out; exams from February 15 to April 4
anam-khan

When will CBSE Board exam 2025 date sheet be released for Class 10, 12?

Latest Question