Find the sum S of the infinite series Σk=1∞ 8·(−2/3)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 8r = −2/3k₀ = 1
S =
2.Easy
The geometric sequence aₙ = 8·0.75ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.01.
a₁ = 8r = 0.75ε = 0.01
n =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ 3ᵏ/k!B: Σ (2/5)ᵏC: Σ (−1)ᵏ/√kD: Σ (3k + 1)/(k + 2)
- 1A: Σ 3ᵏ/k!
- 2B: Σ (2/5)ᵏ
- 3C: Σ (−1)ᵏ/√k
- 4D: Σ (3k + 1)/(k + 2)
4.Medium
Apply the root test to Σk=1∞ ((5k + 3)/(2k + 1))ᵏ. Find L = lim |ak|1/k.
ak = ((5k + 3)/(2k + 1))ᵏ
L =
5.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ·22k+1/(2k + 1)!.
ak = (−1)ᵏ·22k+1/(2k + 1)!
S =
6.Hard
Find the coefficient c₃ of (x − 4)³ in the Taylor series of f(x) = ln x about a = 4.
f(x) = ln xa = 4k = 3
c₃ =
Answer key
- 1. S = −3.2
- 2. n = 25
- 3. D: Σ (3k + 1)/(k + 2)
- 4. L = 2.5
- 5. S = 0.9093
- 6. c₃ = 0.005208
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