Find the sum S7 of the first 7 terms of the geometric sequence 2, 4, 8, …
Sequences & series worksheet with answers
1.Easy
a₁ = 2r = 2n = 7
S7 =
2.Easy
The geometric sequence aₙ = 3·0.8ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.05.
a₁ = 3r = 0.8ε = 0.05
n =
3.Medium
Find the sum S = Σk=1∞ 12/(k(k + 4)).
ak = 12/(k(k + 4))
S =
4.Medium
Find the sum S = Σk=1∞ 12/(k(k + 3)).
ak = 12/(k(k + 3))
S =
5.Hard
Find the coefficient c₄ of (x − 2)⁴ in the Taylor series of f(x) = 1/x about a = 2.
f(x) = 1/xa = 2k = 4
c₄ =
6.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ·0.52k+1/(2k + 1)!.
ak = (−1)ᵏ·0.52k+1/(2k + 1)!
S =
Answer key
- 1. S7 = 254
- 2. n = 20
- 3. S = 6.25
- 4. S = 7.333
- 5. c₄ = 0.03125
- 6. S = 0.4794
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