The geometric sequence aₙ = 20·0.85ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.05.
Sequences & series worksheet with answers
1.Easy
a₁ = 20r = 0.85ε = 0.05
n =
2.Easy
Find the term a38 of the arithmetic sequence 18, 20, 22, 24, …
a₁ = 18d = 2n = 38
a38 =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ (−1)ᵏ/kB: Σ 2/k²C: Σ (3/4)ᵏD: Σ 3ᵏ/k³
- 1A: Σ (−1)ᵏ/k
- 2B: Σ 2/k²
- 3C: Σ (3/4)ᵏ
- 4D: Σ 3ᵏ/k³
4.Medium
Find the sum S = Σk=1∞ 4/(k(k + 1)).
ak = 4/(k(k + 1))
S =
5.Hard
Find the coefficient c₂ of (x − 4)² in the Taylor series of f(x) = √x about a = 4.
f(x) = √xa = 4k = 2
c₂ =
6.Hard
Find the coefficient c₂ of (x − 3)² in the Taylor series of f(x) = ln x about a = 3.
f(x) = ln xa = 3k = 2
c₂ =
Answer key
- 1. n = 38
- 2. a38 = 92
- 3. D: Σ 3ᵏ/k³
- 4. S = 4
- 5. c₂ = −0.01563
- 6. c₂ = −0.05556
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