The geometric sequence aₙ = 8·0.85ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.01.
Sequences & series worksheet with answers
1.Easy
a₁ = 8r = 0.85ε = 0.01
n =
2.Easy
Find the sum S of the infinite series Σk=0∞ 8·(−2/5)ᵏ.
a = 8r = −2/5k₀ = 0
S =
3.Medium
Find the sum S = Σk=1∞ 1/(k(k + 1)).
ak = 1/(k(k + 1))
S =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ (5k + 1)/(k + 2)B: Σ (1/3)ᵏC: Σ 1/(k(k + 2))D: Σ 1/k³
- 1A: Σ (5k + 1)/(k + 2)
- 2B: Σ (1/3)ᵏ
- 3C: Σ 1/(k(k + 2))
- 4D: Σ 1/k³
5.Hard
Use the Maclaurin polynomial of degree 2 of f(x) = cos x to approximate f(−1). Give P₂(−1).
f(x) = cos xn = 2x = −1
P₂(−1) =
6.Hard
Find the coefficient c₃ of (x − 2)³ in the Taylor series of f(x) = ln x about a = 2.
f(x) = ln xa = 2k = 3
c₃ =
Answer key
- 1. n = 43
- 2. S = 5.714
- 3. S = 1
- 4. A: Σ (5k + 1)/(k + 2)
- 5. P₂(−1) = 0.5
- 6. c₃ = 0.04167
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