Find the sum S of the infinite series Σk=1∞ 18·(−3/4)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 18r = −3/4k₀ = 1
S =
2.Easy
Find the sum S9 of the first 9 terms of the geometric sequence 1, 3, 9, …
a₁ = 1r = 3n = 9
S9 =
3.Medium
Find the sum S = Σk=1∞ 4/(k(k + 1)).
ak = 4/(k(k + 1))
S =
4.Medium
Exactly one of the four series converges. Click it.
A: Σ (k + 2)/k²B: Σ 1/(3k + 1)C: Σ (−1)ᵏ/kD: Σ (4k + 1)/(k + 2)
- 1A: Σ (k + 2)/k²
- 2B: Σ 1/(3k + 1)
- 3C: Σ (−1)ᵏ/k
- 4D: Σ (4k + 1)/(k + 2)
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) = cos(−x) to approximate f(1.5). Give P₄(1.5).
f(x) = cos(−x)n = 4x = 1.5
P₄(1.5) =
Answer key
- 1. S = −7.714
- 2. S9 = 9841
- 3. S = 4
- 4. C: Σ (−1)ᵏ/k
- 5. S = 0.3125
- 6. P₄(1.5) = 0.08594
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