Find the sum S8 of the first 8 terms of the geometric sequence 10, 30, 90, …
Sequences & series worksheet with answers
1.Easy
a₁ = 10r = 3n = 8
S8 =
2.Easy
Find the sum S of the infinite series Σk=2∞ 5·(−2/5)ᵏ.
a = 5r = −2/5k₀ = 2
S =
3.Medium
Find the sum S = Σk=1∞ 3/(k(k + 4)).
ak = 3/(k(k + 4))
S =
4.Medium
Find the sum S = Σk=114 1/(k(k + 1)).
ak = 1/(k(k + 1))n = 14
S =
5.Hard
Recognise the series and find its sum: S = Σk=0∞ 0.5ᵏ/k!.
ak = 0.5ᵏ/k!
S =
6.Hard
f(x) = cos x is approximated by its Maclaurin polynomial of degree 4 at x = 0.5. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 1 to find the largest possible error |R₄|.
f(x) = cos xn = 4x = 0.5M = 1
|R₄| =
Answer key
- 1. S8 = 32800
- 2. S = 0.5714
- 3. S = 1.562
- 4. S = 0.9333
- 5. S = 1.649
- 6. |R₄| = 0.0002604
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