Find the sum S8 of the first 8 terms of the geometric sequence 3, 2.4, 1.92, …
Sequences & series worksheet with answers
1.Easy
a₁ = 3r = 0.8n = 8
S8 =
2.Easy
The geometric sequence aₙ = 8·0.6ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.1.
a₁ = 8r = 0.6ε = 0.1
n =
3.Medium
Find the radius of convergence R of the power series Σk=1∞ k·2ᵏ·xᵏ.
Σ k·2ᵏ·xᵏx₀ = 0
R =
4.Medium
Find the sum S = Σk=1∞ 4/(k(k + 2)).
ak = 4/(k(k + 2))
S =
5.Hard
Find the coefficient c₃ of (x − 2)³ in the Taylor series of f(x) = ln x about a = 2.
f(x) = ln xa = 2k = 3
c₃ =
6.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 0.001.
f(x) = cos xx = 2M = 1ε = 0.001
n =
Answer key
- 1. S8 = 12.48
- 2. n = 10
- 3. R = 0.5
- 4. S = 3
- 5. c₃ = 0.04167
- 6. n = 9
Full step-by-step solutions: practise this topic on examproblems.com.