Find the sum S8 of the first 8 terms of the geometric sequence 10, 8, 6.4, …
Sequences & series worksheet with answers
1.Easy
a₁ = 10r = 0.8n = 8
S8 =
2.Easy
Find the term a20 of the arithmetic sequence 5, 10, 15, 20, …
a₁ = 5d = 5n = 20
a20 =
3.Medium
Find the sum S = Σk=1∞ 6/(k(k + 4)).
ak = 6/(k(k + 4))
S =
4.Medium
Apply the ratio test to Σk=1∞ k!/kᵏ. Find L = lim |ak+1/ak|.
ak = k!/kᵏ
L =
5.Hard
f(x) = cos 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 0.0005.
f(x) = cos xx = 2M = 1ε = 0.0005
n =
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 0.0001.
f(x) = cos xx = 0.5M = 1ε = 0.0001
n =
Answer key
- 1. S8 = 41.61
- 2. a20 = 100
- 3. S = 3.125
- 4. L = 0.3679
- 5. n = 9
- 6. n = 5
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