Find the sum S7 of the first 7 terms of the geometric sequence 3, −1.5, 0.75, …
Sequences & series worksheet with answers
1.Easy
a₁ = 3r = −0.5n = 7
S7 =
2.Easy
Find the sum S9 of the first 9 terms of the arithmetic sequence 10, 15, 20, 25, …
a₁ = 10d = 5n = 9
S9 =
3.Medium
Apply the ratio test to Σk=1∞ kᵏ/(2ᵏ·k!). Find L = lim |ak+1/ak|.
ak = kᵏ/(2ᵏ·k!)
L =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ k!/2ᵏB: Σ (1/2)ᵏC: Σ 3/k²D: Σ 1/(k(k + 2))
- 1A: Σ k!/2ᵏ
- 2B: Σ (1/2)ᵏ
- 3C: Σ 3/k²
- 4D: Σ 1/(k(k + 2))
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 1 × 10⁻⁶.
f(x) = eˣx = 2M = 8ε = 1 × 10⁻⁶
n =
6.Hard
f(x) = cos 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 × 10⁻⁵.
f(x) = cos xx = 0.5M = 1ε = 1 × 10⁻⁵
n =
Answer key
- 1. S7 = 2.016
- 2. S9 = 270
- 3. L = 1.359
- 4. A: Σ k!/2ᵏ
- 5. n = 14
- 6. n = 6
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