The geometric sequence aₙ = 10·0.5ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.2.
Sequences & series worksheet with answers
1.Easy
a₁ = 10r = 0.5ε = 0.2
n =
2.Easy
Find the sum S7 of the first 7 terms of the geometric sequence 4, 8, 16, …
a₁ = 4r = 2n = 7
S7 =
3.Medium
Apply the ratio test to Σk=1∞ 3ᵏ·k!/kᵏ. Find L = lim |ak+1/ak|.
ak = 3ᵏ·k!/kᵏ
L =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ 5/k²B: Σ 1/kC: Σ (−1)ᵏ/√kD: Σ k²/5ᵏ
- 1A: Σ 5/k²
- 2B: Σ 1/k
- 3C: Σ (−1)ᵏ/√k
- 4D: Σ k²/5ᵏ
5.Hard
f(x) = cos x is approximated at x = 1 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 = 1M = 1ε = 0.0005
n =
6.Hard
Find the coefficient c₄ of (x − 2)⁴ in the Taylor series of f(x) = ln x about a = 2.
f(x) = ln xa = 2k = 4
c₄ =
Answer key
- 1. n = 7
- 2. S7 = 508
- 3. L = 1.104
- 4. B: Σ 1/k
- 5. n = 6
- 6. c₄ = −0.01563
Full step-by-step solutions: practise this topic on examproblems.com.