The geometric sequence aₙ = 8·0.6ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.01.
Sequences & series worksheet with answers
1.Easy
a₁ = 8r = 0.6ε = 0.01
n =
2.Easy
The geometric sequence aₙ = 3·0.6ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.5.
a₁ = 3r = 0.6ε = 0.5
n =
3.Medium
Find the sum S = Σk=1∞ 1/(k(k + 2)).
ak = 1/(k(k + 2))
S =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ (−1)ᵏ/√kB: Σ 3ᵏ/k!C: Σ 1/(4k + 1)D: Σ 5/k³
- 1A: Σ (−1)ᵏ/√k
- 2B: Σ 3ᵏ/k!
- 3C: Σ 1/(4k + 1)
- 4D: Σ 5/k³
5.Hard
Recognise the series and find its sum: S = Σk=1∞ k·0.2ᵏ.
ak = k·0.2ᵏ
S =
6.Hard
Use the Maclaurin polynomial of degree 4 of f(x) = e−x to approximate f(1.5). Give P₄(1.5).
f(x) = e−xn = 4x = 1.5
P₄(1.5) =
Answer key
- 1. n = 15
- 2. n = 5
- 3. S = 0.75
- 4. C: Σ 1/(4k + 1)
- 5. S = 0.3125
- 6. P₄(1.5) = 0.2734
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