The geometric sequence aₙ = 8·0.6ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.1.
Sequences & series worksheet with answers
1.Easy
a₁ = 8r = 0.6ε = 0.1
n =
2.Easy
Find the sum S of the infinite series Σk=2∞ 5·(1/4)ᵏ.
a = 5r = 1/4k₀ = 2
S =
3.Medium
Find the radius of convergence R of the power series Σk=1∞ 4ᵏx²ᵏ/k.
Σ 4ᵏx²ᵏ/kx₀ = 0
R =
4.Medium
Exactly one of the four series converges. Click it.
A: Σ (1/3)ᵏB: Σ (1 + 1/k)ᵏC: Σ (7/4)ᵏD: Σ 1/k
- 1A: Σ (1/3)ᵏ
- 2B: Σ (1 + 1/k)ᵏ
- 3C: Σ (7/4)ᵏ
- 4D: Σ 1/k
5.Hard
Recognise the series and find its sum: S = Σk=0∞ 0.5ᵏ/k!.
ak = 0.5ᵏ/k!
S =
6.Hard
f(x) = ln(1 + x) is approximated by its Maclaurin polynomial of degree 3 at x = 0.3. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 3! = 6 to find the largest possible error |R₃|.
f(x) = ln(1 + x)n = 3x = 0.3M = 6
|R₃| =
Answer key
- 1. n = 10
- 2. S = 0.4167
- 3. R = 0.5
- 4. A: Σ (1/3)ᵏ
- 5. S = 1.649
- 6. |R₃| = 0.002025
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