Check sibling questions

Ex 9.3, 4 - Chapter 9 Class 11 Sequences and Series (Term 1)

Last updated at March 30, 2023 by

Ex 9.3, 4 - The 4th term of GP is square of its second term - Geometric Progression(GP): Formulae based

Ex 9.3, 4 - Chapter 9 Class 11 Sequences and Series - Part 2
Ex 9.3, 4 - Chapter 9 Class 11 Sequences and Series - Part 3

Get live Maths 1-on-1 Classs - Class 6 to 12

Book 30 minute class for ₹ 499 ₹ 299

Transcript

Ex 9.3,4 The 4th term of a G.P. is square of its second term, and the first term is 3. Determine its 7th term. We know that an = arn 1 where an = nth term of GP n is the number of terms a is the first term r is the common ratio Here, First term = a = 3 Also, 4th term of G.P = (2nd term of G.P.)2 i.e. a4 = (a2)2 Putting values in (1) ar4 1 = (ar2 1)2 ar3 = (ar1)2 ar3 = (ar)2 ar3 = a2 r2 ^3/ ^2 = ^2/ ^(3 2) = ^(2 1) r1 = a1 r = a Putting a = -3 r = -3 Thus, r = -3 & a = -3 Now we need to find 7th term, we use the formula an = arn 1 Putting n = 7 , a = 3, r = 3 a7 = ( 3) ( 3)7 1 = ( 3) ( 3)6 = (-3) 729 = 2187 Hence, 7th term is 2187

Ask a doubt
Davneet Singh's photo - Co-founder, Teachoo

Made by

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.