Find the term a17 of the arithmetic sequence 11, 16, 21, 26, …
Sequences & series worksheet with answers
1.Easy
a₁ = 11d = 5n = 17
a17 =
2.Easy
The geometric sequence aₙ = 8·0.75ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.1.
a₁ = 8r = 0.75ε = 0.1
n =
3.Medium
Find the sum S = Σk=1∞ 2/(k(k + 3)).
ak = 2/(k(k + 3))
S =
4.Medium
Find the radius of convergence R of the power series Σk=1∞ k!·(x − 1)ᵏ/kᵏ.
Σ k!·(x − 1)ᵏ/kᵏx₀ = 1
R =
5.Hard
f(x) = eˣ is approximated at x = 2 by its Maclaurin polynomial of degree n. With the Lagrange bound M·|x|ⁿ⁺¹/(n + 1)! and M = 8, find the smallest degree n that guarantees an error below 1 × 10⁻⁵.
f(x) = eˣx = 2M = 8ε = 1 × 10⁻⁵
n =
6.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ·1.22k/(2k)!.
ak = (−1)ᵏ·1.22k/(2k)!
S =
Answer key
- 1. a17 = 91
- 2. n = 17
- 3. S = 1.222
- 4. R = 2.718
- 5. n = 13
- 6. S = 0.3624
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