Find the sum S5 of the first 5 terms of the geometric sequence 1, 0.5, 0.25, …
Sequences & series worksheet with answers
1.Easy
a₁ = 1r = 0.5n = 5
S5 =
2.Easy
Find the sum S of the infinite series Σk=2∞ 12·(−2/5)ᵏ.
a = 12r = −2/5k₀ = 2
S =
3.Medium
Find the radius of convergence R of the power series Σk=1∞ xᵏ/3ᵏ.
Σ xᵏ/3ᵏx₀ = 0
R =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ k/2ᵏB: Σ (−1)ᵏ/√kC: Σ 2ᵏ/k³D: Σ 1/(2ᵏ + k)
- 1A: Σ k/2ᵏ
- 2B: Σ (−1)ᵏ/√k
- 3C: Σ 2ᵏ/k³
- 4D: Σ 1/(2ᵏ + k)
5.Hard
f(x) = eˣ 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 = 2, find the smallest degree n that guarantees an error below 0.001.
f(x) = eˣx = 0.5M = 2ε = 0.001
n =
6.Hard
f(x) = eˣ is approximated at x = 1 by its Maclaurin polynomial of degree n. With the Lagrange bound M·|x|ⁿ⁺¹/(n + 1)! and M = 3, find the smallest degree n that guarantees an error below 1 × 10⁻⁶.
f(x) = eˣx = 1M = 3ε = 1 × 10⁻⁶
n =
Answer key
- 1. S5 = 1.938
- 2. S = 1.371
- 3. R = 3
- 4. C: Σ 2ᵏ/k³
- 5. n = 4
- 6. n = 9
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