Find the sum S of the infinite series Σk=0∞ 6·(4/5)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 6r = 4/5k₀ = 0
S =
2.Easy
Find the sum S of the infinite series Σk=0∞ 12·(1/2)ᵏ.
a = 12r = 1/2k₀ = 0
S =
3.Medium
Apply the root test to Σk=1∞ ((3k + 5)/(5k + 5))ᵏ. Find L = lim |ak|1/k.
ak = ((3k + 5)/(5k + 5))ᵏ
L =
4.Medium
Apply the ratio test to Σk=1∞ k·2ᵏ/3ᵏ. Find L = lim |ak+1/ak|.
ak = k·2ᵏ/3ᵏ
L =
5.Hard
f(x) = cos x is approximated at x = 1.5 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 1 × 10⁻⁶.
f(x) = cos xx = 1.5M = 1ε = 1 × 10⁻⁶
n =
6.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ/(2k)!.
ak = (−1)ᵏ/(2k)!
S =
Answer key
- 1. S = 30
- 2. S = 24
- 3. L = 0.6
- 4. L = 0.6667
- 5. n = 11
- 6. S = 0.5403
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