Find the sum S of the infinite series Σk=0∞ 9·(4/5)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 9r = 4/5k₀ = 0
S =
2.Easy
A ball is dropped and its first rebound reaches 10 m. Every next rebound reaches 85% of the previous one. Which rebound n is the first one lower than 0.01 m?
a₁ = 10r = 0.85ε = 0.01
n =
3.Medium
Apply the ratio test to Σk=1∞ (k!)²·1ᵏ/(2k)!. Find L = lim |ak+1/ak|.
ak = (k!)²·1ᵏ/(2k)!
L =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ (−1)ᵏ/kB: Σ k/2ᵏC: Σ 1/(k² + 4)D: Σ 2/k
- 1A: Σ (−1)ᵏ/k
- 2B: Σ k/2ᵏ
- 3C: Σ 1/(k² + 4)
- 4D: Σ 2/k
5.Hard
f(x) = eˣ is approximated at x = 2 by its Maclaurin polynomial of degree n. With the Lagrange bound M·|x|ⁿ⁺¹/(n + 1)! and M = 8, find the smallest degree n that guarantees an error below 0.001.
f(x) = eˣx = 2M = 8ε = 0.001
n =
6.Hard
Use the Maclaurin polynomial of degree 2 of f(x) = e0.5x to approximate f(2.5). Give P₂(2.5).
f(x) = e0.5xn = 2x = 2.5
P₂(2.5) =
Answer key
- 1. S = 45
- 2. n = 44
- 3. L = 0.25
- 4. D: Σ 2/k
- 5. n = 10
- 6. P₂(2.5) = 3.031
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