The geometric sequence aₙ = 3·0.85ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.05.
Sequences & series worksheet with answers
1.Easy
a₁ = 3r = 0.85ε = 0.05
n =
2.Easy
The arithmetic sequence −7, −6.5, −6, −5.5, … ends with the term 2.5. How many terms n does it have?
a₁ = −7d = 0.5aₙ = 2.5
n =
3.Medium
Apply the ratio test to Σk=1∞ k·3ᵏ/4ᵏ. Find L = lim |ak+1/ak|.
ak = k·3ᵏ/4ᵏ
L =
4.Medium
Exactly one of the four series converges. Click it.
A: Σ (−1)ᵏ/kB: Σ (4k + 1)/(k + 2)C: Σ 2ᵏ/k²D: Σ 1/√k
- 1A: Σ (−1)ᵏ/k
- 2B: Σ (4k + 1)/(k + 2)
- 3C: Σ 2ᵏ/k²
- 4D: Σ 1/√k
5.Hard
Use the Maclaurin polynomial of degree 3 of f(x) = ln(1 + x) to approximate f(0.5). Give P₃(0.5).
f(x) = ln(1 + x)n = 3x = 0.5
P₃(0.5) =
6.Hard
Use the Maclaurin polynomial of degree 3 of f(x) = 1/(1 − x) to approximate f(0.5). Give P₃(0.5).
f(x) = 1/(1 − x)n = 3x = 0.5
P₃(0.5) =
Answer key
- 1. n = 27
- 2. n = 20
- 3. L = 0.75
- 4. A: Σ (−1)ᵏ/k
- 5. P₃(0.5) = 0.4167
- 6. P₃(0.5) = 1.875
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