Infinite series doubt

JEE Main 2015 Answers › Algebra questions › Infinite series doubt

If S_n=(1.2)/3! + (2.2²)/4! + (3.2³)/5! +...............upto n terms.

Then find sum of infinite terms.

#Mathematics #Algebra

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7 Answers

1

Athenes Analyst ·2011-11-30 13:19:48

options:
a)4/227
b)3/e
c)227/3
d)1

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262

Aditya Bhutra ·2011-11-30 21:13:21

i am getting d)1 . please confirm.

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Athenes Analyst ·2011-11-30 23:13:01

Tell me the method! My friend gave this question to me and he ticked d)1 as answer so probably that is right answer!

I am getting some complex answer in terms of e²

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Aditya Bhutra ·2011-12-01 01:43:39

okay, i am just providing u with a hint.

use expansion of e^x. divide both sides with x² and then just some calculus.

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Athenes Analyst ·2011-12-01 14:34:42

Ok thanks! :D

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Athenes Analyst ·2011-12-03 06:54:29

Did you get 1? i tried 3 times (Which is foolishness) and everytime I get 1/2 not 1.

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Aditya Bhutra ·2011-12-03 07:17:07

i think u r making a silly mistake, just recheck the given series
(notice that each term has been multiplied by 2)

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Your Answer

Basic Integral Calculus Operators Symbols Matrix Cases

√ √ || {} [] () → ~ ^ x x x → → ln log lg lim lim cos sin tan cot arcsin arccos arctan

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∑ ∑ ∑ ∑ ∑ ∮ ∮ ∮ ∮ ∮ ∏ ∏ ∏ ∏ ∏ ∐ ∐ ∐ ∐ ∐

+ - × ÷ ± ∓ = ∪ ∩ ≠ ∼ ≈ ∅ ∀ ∃ ∈ ∋ ∝ ≤ ≥ ≃ ≅ ≡ < > ≪ ≫ ⊂ ∉ ⊃ ⊆ ⊇ ⇒ ⇐ ⇔ ⇒ ⇐ ⇔ ⇑ ⇓ ⇕ → ← ↔ → ← ↔ ↑ ↓ ↕ ↖ ↗ ↘ ↙ ↪ ↩ ⇀ ↼ ⇁ ↽

° ∂ ∞ α β γ δ θ λ μ ν ξ π ρ σ φ ω ε ƒ κ τ υ Γ Δ Λ Σ Π Ω