The geometric sequence aₙ = 3·0.6ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.2.
Sequences & series worksheet with answers
1.Easy
a₁ = 3r = 0.6ε = 0.2
n =
2.Easy
A ball is dropped and its first rebound reaches 3 m. Every next rebound reaches 50% of the previous one. Which rebound n is the first one lower than 0.01 m?
a₁ = 3r = 0.5ε = 0.01
n =
3.Medium
Exactly one of the four series converges. Click it.
A: Σ k/(k + 7)B: Σ (−1)ᵏ/√kC: Σ ln k / kD: Σ (4/3)ᵏ
- 1A: Σ k/(k + 7)
- 2B: Σ (−1)ᵏ/√k
- 3C: Σ ln k / k
- 4D: Σ (4/3)ᵏ
4.Medium
Find the radius of convergence R of the power series Σk=1∞ 16ᵏx²ᵏ/k.
Σ 16ᵏx²ᵏ/kx₀ = 0
R =
5.Hard
Find the coefficient c₂ of (x + 1)² in the Taylor series of f(x) = e−x about a = −1.
f(x) = e−xa = −1k = 2
c₂ =
6.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ/(2k + 1)!.
ak = (−1)ᵏ/(2k + 1)!
S =
Answer key
- 1. n = 7
- 2. n = 10
- 3. B: Σ (−1)ᵏ/√k
- 4. R = 0.25
- 5. c₂ = 1.359
- 6. S = 0.8415
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