Find the sum S23 of the first 23 terms of the arithmetic sequence −8, −6, −4, −2, …
Sequences & series worksheet with answers
1.Easy
a₁ = −8d = 2n = 23
S23 =
2.Easy
The arithmetic sequence 10, 7, 4, 1, … ends with the term −77. How many terms n does it have?
a₁ = 10d = −3aₙ = −77
n =
3.Medium
Find the radius of convergence R of the power series Σk=1∞ 4ᵏx²ᵏ/k.
Σ 4ᵏx²ᵏ/kx₀ = 0
R =
4.Medium
Exactly one of the four series converges. Click it.
A: Σ (1/3)ᵏB: Σ ln k / kC: Σ 1/(4k + 3)D: Σ k/(k + 5)
- 1A: Σ (1/3)ᵏ
- 2B: Σ ln k / k
- 3C: Σ 1/(4k + 3)
- 4D: Σ k/(k + 5)
5.Hard
Use the Maclaurin polynomial of degree 5 of f(x) = sin x to approximate f(2.5). Give P₅(2.5).
f(x) = sin xn = 5x = 2.5
P₅(2.5) =
6.Hard
f(x) = cos x is approximated by its Maclaurin polynomial of degree 5 at x = 0.3. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 1 to find the largest possible error |R₅|.
f(x) = cos xn = 5x = 0.3M = 1
|R₅| =
Answer key
- 1. S23 = 322
- 2. n = 30
- 3. R = 0.5
- 4. A: Σ (1/3)ᵏ
- 5. P₅(2.5) = 0.7096
- 6. |R₅| = 1.012 × 10⁻⁶
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