Find the sum S8 of the first 8 terms of the geometric sequence 1, 0.8, 0.64, …
Sequences & series worksheet with answers
1.Easy
a₁ = 1r = 0.8n = 8
S8 =
2.Easy
Find the sum S of the infinite series Σk=1∞ 9·(−2/3)ᵏ.
a = 9r = −2/3k₀ = 1
S =
3.Medium
Apply the ratio test to Σk=1∞ (k!)²·8ᵏ/(2k)!. Find L = lim |ak+1/ak|.
ak = (k!)²·8ᵏ/(2k)!
L =
4.Medium
Apply the root test to Σk=1∞ ((4k + 1)/(3k + 4))ᵏ. Find L = lim |ak|1/k.
ak = ((4k + 1)/(3k + 4))ᵏ
L =
5.Hard
Recognise the series and find its sum: S = Σk=1∞ (−1)k+1·0.75ᵏ/k.
ak = (−1)k+1·0.75ᵏ/k
S =
6.Hard
f(x) = sin x is approximated at x = 2 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 × 10⁻⁵.
f(x) = sin xx = 2M = 1ε = 1 × 10⁻⁵
n =
Answer key
- 1. S8 = 4.161
- 2. S = −3.6
- 3. L = 2
- 4. L = 1.333
- 5. S = 0.5596
- 6. n = 11
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