The geometric sequence aₙ = 20·0.9ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.2.
Sequences & series worksheet with answers
1.Easy
a₁ = 20r = 0.9ε = 0.2
n =
2.Easy
Find the sum S11 of the first 11 terms of the arithmetic sequence 2, 6, 10, 14, …
a₁ = 2d = 4n = 11
S11 =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ k²/3ᵏB: Σ 2/k²C: Σ 1/(k(k + 4))D: Σ ln k / k
- 1A: Σ k²/3ᵏ
- 2B: Σ 2/k²
- 3C: Σ 1/(k(k + 4))
- 4D: Σ ln k / k
4.Medium
Find the sum S = Σk=1∞ 5/(k(k + 1)).
ak = 5/(k(k + 1))
S =
5.Hard
f(x) = sin x is approximated by its Maclaurin polynomial of degree 2 at x = 0.3. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 1 to find the largest possible error |R₂|.
f(x) = sin xn = 2x = 0.3M = 1
|R₂| =
6.Hard
f(x) = eˣ is approximated by its Maclaurin polynomial of degree 5 at x = 0.8. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = e0.8 = 2.226 to find the largest possible error |R₅|.
f(x) = eˣn = 5x = 0.8M = 2.226
|R₅| =
Answer key
- 1. n = 45
- 2. S11 = 242
- 3. D: Σ ln k / k
- 4. S = 5
- 5. |R₂| = 0.0045
- 6. |R₅| = 0.0008103
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