Find the sum S7 of the first 7 terms of the geometric sequence 4, 2, 1, …
Sequences & series worksheet with answers
1.Easy
a₁ = 4r = 0.5n = 7
S7 =
2.Easy
The geometric sequence aₙ = 2·0.85ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.1.
a₁ = 2r = 0.85ε = 0.1
n =
3.Medium
Exactly one of the four series converges. Click it.
A: Σ 3/k³B: Σ 3ᵏ/k³C: Σ (k + 3)/k²D: Σ (3/2)ᵏ
- 1A: Σ 3/k³
- 2B: Σ 3ᵏ/k³
- 3C: Σ (k + 3)/k²
- 4D: Σ (3/2)ᵏ
4.Medium
Apply the ratio test to Σk=1∞ (k!)²·5ᵏ/(2k)!. Find L = lim |ak+1/ak|.
ak = (k!)²·5ᵏ/(2k)!
L =
5.Hard
Use the Maclaurin polynomial of degree 3 of f(x) = ln(1 + 2x) to approximate f(0.25). Give P₃(0.25).
f(x) = ln(1 + 2x)n = 3x = 0.25
P₃(0.25) =
6.Hard
Find the coefficient c₂ of (x − 1)² in the Taylor series of f(x) = ∛x about a = 1.
f(x) = ∛xa = 1k = 2
c₂ =
Answer key
- 1. S7 = 7.938
- 2. n = 20
- 3. A: Σ 3/k³
- 4. L = 1.25
- 5. P₃(0.25) = 0.4167
- 6. c₂ = −0.1111
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