Find the sum S6 of the first 6 terms of the geometric sequence 5, 4, 3.2, …
Sequences & series worksheet with answers
1.Easy
a₁ = 5r = 0.8n = 6
S6 =
2.Easy
Find the term a38 of the arithmetic sequence 6, 7.5, 9, 10.5, …
a₁ = 6d = 1.5n = 38
a38 =
3.Medium
Apply the ratio test to Σk=1∞ k!/kᵏ. Find L = lim |ak+1/ak|.
ak = k!/kᵏ
L =
4.Medium
Find the sum S = Σk=126 5/(k(k + 1)).
ak = 5/(k(k + 1))n = 26
S =
5.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ·1.22k/(2k)!.
ak = (−1)ᵏ·1.22k/(2k)!
S =
6.Hard
f(x) = sin x is approximated by its Maclaurin polynomial of degree 5 at x = 0.5. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 1 to find the largest possible error |R₅|.
f(x) = sin xn = 5x = 0.5M = 1
|R₅| =
Answer key
- 1. S6 = 18.45
- 2. a38 = 61.5
- 3. L = 0.3679
- 4. S = 4.815
- 5. S = 0.3624
- 6. |R₅| = 2.17 × 10⁻⁵
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