Find the sum S8 of the first 8 terms of the geometric sequence 10, 15, 22.5, …
Sequences & series worksheet with answers
1.Easy
a₁ = 10r = 1.5n = 8
S8 =
2.Easy
Find the sum S of the infinite series Σk=2∞ 10·(−1/2)ᵏ.
a = 10r = −1/2k₀ = 2
S =
3.Medium
Apply the ratio test to Σk=1∞ 2ᵏ·k!/kᵏ. Find L = lim |ak+1/ak|.
ak = 2ᵏ·k!/kᵏ
L =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ (−1)ᵏ/√kB: Σ 1/(k² + 6)C: Σ (4/3)ᵏD: Σ (3/5)ᵏ
- 1A: Σ (−1)ᵏ/√k
- 2B: Σ 1/(k² + 6)
- 3C: Σ (4/3)ᵏ
- 4D: Σ (3/5)ᵏ
5.Hard
f(x) = sin x is approximated at x = 1 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 0.001.
f(x) = sin xx = 1M = 1ε = 0.001
n =
6.Hard
f(x) = sin x is approximated at x = 1 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 = 1M = 1ε = 1 × 10⁻⁶
n =
Answer key
- 1. S8 = 492.6
- 2. S = 1.667
- 3. L = 0.7358
- 4. C: Σ (4/3)ᵏ
- 5. n = 6
- 6. n = 9
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