Find the sum S of the infinite series Σk=1∞ 9·(1/4)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 9r = 1/4k₀ = 1
S =
2.Easy
A ball is dropped and its first rebound reaches 8 m. Every next rebound reaches 50% of the previous one. Which rebound n is the first one lower than 0.1 m?
a₁ = 8r = 0.5ε = 0.1
n =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ 3ᵏ/k²B: Σ k²/5ᵏC: Σ (−1)ᵏ/kD: Σ (4/5)ᵏ
- 1A: Σ 3ᵏ/k²
- 2B: Σ k²/5ᵏ
- 3C: Σ (−1)ᵏ/k
- 4D: Σ (4/5)ᵏ
4.Medium
Apply the ratio test to Σk=1∞ k²·2ᵏ/3ᵏ. Find L = lim |ak+1/ak|.
ak = k²·2ᵏ/3ᵏ
L =
5.Hard
Use the Maclaurin polynomial of degree 2 of f(x) = cos x to approximate f(1.2). Give P₂(1.2).
f(x) = cos xn = 2x = 1.2
P₂(1.2) =
6.Hard
Recognise the series and find its sum: S = Σk=0∞ 2ᵏ/k!.
ak = 2ᵏ/k!
S =
Answer key
- 1. S = 3
- 2. n = 8
- 3. A: Σ 3ᵏ/k²
- 4. L = 0.6667
- 5. P₂(1.2) = 0.28
- 6. S = 7.389
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