Find the sum S of the infinite series Σk=0∞ 9·(2/3)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 9r = 2/3k₀ = 0
S =
2.Easy
Find the sum S7 of the first 7 terms of the geometric sequence 10, 20, 40, …
a₁ = 10r = 2n = 7
S7 =
3.Medium
Find the radius of convergence R of the power series Σk=1∞ (x + 1)ᵏ/2ᵏ.
Σ (x + 1)ᵏ/2ᵏx₀ = −1
R =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ (−1)ᵏ/√kB: Σ 5/k⁴C: Σ 1/√kD: Σ 1/(k² + 8)
- 1A: Σ (−1)ᵏ/√k
- 2B: Σ 5/k⁴
- 3C: Σ 1/√k
- 4D: Σ 1/(k² + 8)
5.Hard
Use the Maclaurin polynomial of degree 4 of f(x) = 1/(1 + x) to approximate f(0.5). Give P₄(0.5).
f(x) = 1/(1 + x)n = 4x = 0.5
P₄(0.5) =
6.Hard
Recognise the series and find its sum: S = Σk=0∞ 0.5ᵏ/k!.
ak = 0.5ᵏ/k!
S =
Answer key
- 1. S = 27
- 2. S7 = 1270
- 3. R = 2
- 4. C: Σ 1/√k
- 5. P₄(0.5) = 0.6875
- 6. S = 1.649
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