Find the sum S11 of the first 11 terms of the arithmetic sequence 1, 7, 13, 19, …
Sequences & series worksheet with answers
1.Easy
a₁ = 1d = 6n = 11
S11 =
2.Easy
Find the sum S of the infinite series Σk=1∞ 18·(−1/4)ᵏ.
a = 18r = −1/4k₀ = 1
S =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ (2/3)ᵏB: Σ 1/(k(k + 1))C: Σ 1/√kD: Σ 2ᵏ/k!
- 1A: Σ (2/3)ᵏ
- 2B: Σ 1/(k(k + 1))
- 3C: Σ 1/√k
- 4D: Σ 2ᵏ/k!
4.Medium
Find the sum S = Σk=137 3/(k(k + 1)).
ak = 3/(k(k + 1))n = 37
S =
5.Hard
Recognise the series and find its sum: S = Σk=1∞ k·0.2ᵏ.
ak = k·0.2ᵏ
S =
6.Hard
f(x) = cos x is approximated at x = 0.5 by its Maclaurin polynomial of degree n. With the Lagrange bound M·|x|ⁿ⁺¹/(n + 1)! and M = 1, find the smallest degree n that guarantees an error below 0.0005.
f(x) = cos xx = 0.5M = 1ε = 0.0005
n =
Answer key
- 1. S11 = 341
- 2. S = −3.6
- 3. C: Σ 1/√k
- 4. S = 2.921
- 5. S = 0.3125
- 6. n = 4
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