Find the sum S of the infinite series Σk=2∞ 2·(−3/4)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 2r = −3/4k₀ = 2
S =
2.Easy
The geometric sequence aₙ = 5·0.85ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.2.
a₁ = 5r = 0.85ε = 0.2
n =
3.Medium
Find the sum S = Σk=1∞ 1/(k(k + 1)).
ak = 1/(k(k + 1))
S =
4.Medium
Exactly one of the four series converges. Click it.
A: Σ k/(k + 9)B: Σ k!/10ᵏC: Σ (5/4)ᵏD: Σ (−1)ᵏ/k
- 1A: Σ k/(k + 9)
- 2B: Σ k!/10ᵏ
- 3C: Σ (5/4)ᵏ
- 4D: Σ (−1)ᵏ/k
5.Hard
Find the coefficient c₄ of (x − 1)⁴ in the Taylor series of f(x) = 1/x about a = 1.
f(x) = 1/xa = 1k = 4
c₄ =
6.Hard
f(x) = eˣ is approximated by its Maclaurin polynomial of degree 3 at x = 1.5. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = e1.5 = 4.482 to find the largest possible error |R₃|.
f(x) = eˣn = 3x = 1.5M = 4.482
|R₃| =
Answer key
- 1. S = 0.6429
- 2. n = 21
- 3. S = 1
- 4. D: Σ (−1)ᵏ/k
- 5. c₄ = 1
- 6. |R₃| = 0.9454
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