JEE Main 2021 — Sequences And Series Question with Solution
From: JEE Main 2021 (Online) 26th August Morning Shift
Question
If the sum of an infinite GP a, ar, ar2, ar3, ....... is 15 and the sum of the squares of its each term is 150, then the sum of ar2, ar4, ar6, ....... is :
Choose an option
Show full solutionCorrect option: B
Correct answer
B
Step-by-step explanation
Sum of infinite terms :
..... (i)
Series formed by square of terms :
a2, a2r2, a2r4, a2r6 .......
Sum =
...... (ii)
by (i) and (ii), a = 12; r =
Now, series : ar2, ar4, ar6
Sum =
..... (i)
Series formed by square of terms :
a2, a2r2, a2r4, a2r6 .......
Sum =
...... (ii)
by (i) and (ii), a = 12; r =
Now, series : ar2, ar4, ar6
Sum =
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