Find the sum S7 of the first 7 terms of the geometric sequence 10, 20, 40, …
Sequences & series worksheet with answers
1.Easy
a₁ = 10r = 2n = 7
S7 =
2.Easy
Find the sum S9 of the first 9 terms of the geometric sequence 1, 2, 4, …
a₁ = 1r = 2n = 9
S9 =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ (−1)ᵏ/√kB: Σ 3ᵏ/k!C: Σ 1/(k² + 4)D: Σ k/(k + 9)
- 1A: Σ (−1)ᵏ/√k
- 2B: Σ 3ᵏ/k!
- 3C: Σ 1/(k² + 4)
- 4D: Σ k/(k + 9)
4.Medium
Exactly one of the four series converges. Click it.
A: Σ 5/k⁴B: Σ 2ᵏ/k³C: Σ ln k / kD: Σ 1/(3k + 7)
- 1A: Σ 5/k⁴
- 2B: Σ 2ᵏ/k³
- 3C: Σ ln k / k
- 4D: Σ 1/(3k + 7)
5.Hard
Find the coefficient c₃ of (x − 4)³ in the Taylor series of f(x) = 1/x about a = 4.
f(x) = 1/xa = 4k = 3
c₃ =
6.Hard
f(x) = sin x is approximated at x = 0.5 by its Maclaurin polynomial of degree n. With the Lagrange bound M·|x|ⁿ⁺¹/(n + 1)! and M = 1, find the smallest degree n that guarantees an error below 1 × 10⁻⁶.
f(x) = sin xx = 0.5M = 1ε = 1 × 10⁻⁶
n =
Answer key
- 1. S7 = 1270
- 2. S9 = 511
- 3. D: Σ k/(k + 9)
- 4. A: Σ 5/k⁴
- 5. c₃ = −0.003906
- 6. n = 7
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