Find the sum S6 of the first 6 terms of the geometric sequence 2, −6, 18, …
Sequences & series worksheet with answers
1.Easy
a₁ = 2r = −3n = 6
S6 =
2.Easy
Find the sum S of the infinite series Σk=1∞ 10·(1/3)ᵏ.
a = 10r = 1/3k₀ = 1
S =
3.Medium
Find the sum S = Σk=1∞ 6/(k(k + 3)).
ak = 6/(k(k + 3))
S =
4.Medium
Find the sum S = Σk=1∞ 2/(k(k + 3)).
ak = 2/(k(k + 3))
S =
5.Hard
Recognise the series and find its sum: S = Σk=0∞ 3ᵏ/k!.
ak = 3ᵏ/k!
S =
6.Hard
f(x) = cos x is approximated at x = 1 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 1 × 10⁻⁶.
f(x) = cos xx = 1M = 1ε = 1 × 10⁻⁶
n =
Answer key
- 1. S6 = −364
- 2. S = 5
- 3. S = 3.667
- 4. S = 1.222
- 5. S = 20.09
- 6. n = 9
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