SOLUTION: THE SUM OF AN INFINITE GEOMETRIC PROGRESSION IS 15 AND THE SUM OF THE SQUARES OF THESE TERMS IS 45. FIND THE SERIES.
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Question 941784: THE SUM OF AN INFINITE GEOMETRIC PROGRESSION IS 15 AND THE SUM OF THE SQUARES OF THESE TERMS IS 45. FIND THE SERIES.
Answer by srinivas.g(540) (Show Source): You can put this solution on YOUR website!
The formula for sum of infinite GP is
hence ..........eq(1)
HE SUM OF THE SQUARES OF THESE TERMS IS 45
hence ......eq(2)
divide eq(1) with eq (2)
move (1+r) to the right
but from eq(1)
move (1-r) to the right
from above expressions
3+3*r= 15*1-r*15
3+3r =15-15r
move -15r to the left
3+3r+15r =15
3+18r =15
18r =15-3
18r =12
r =
r=
but a = (1+r)*3
=
=
=
= 5
a= 5, r= 2/3
series = 5, 10/3, 20/9,...
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