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Find 3 +6+11+20+37+70+135 upto n terms. Please since it using sequence and series chapter, method of difference topic And explain me how to solve it when the difference is in gp

Find 3 +6+11+20+37+70+135 upto n terms.
Please since it using sequence and series chapter, method of difference topic
And explain me how to solve it when the difference is in gp

Grade:11

1 Answers

Arun
25750 Points
5 years ago
Dear student
 
difference
 
3, 5, 9, 17,  33, 65, …...
 
again difference
 
2, 4, 8, 16, 32
 
now diffrence is in G.P. with common ratio as 2
 
hence
Tn = a r^n + bn + c
 
put n = 1, 2, 3 to find a, b,c
 
then you can simply use sigma to find sum.
 
T1 = 3 = 2a + b + c
 
T2 = 6 = 4a + 2b + c
 
T3 = 11 = 8a + 3b + c
 
 

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