The arithmetic sequence −3, −7, −11, −15, … ends with the term −39. How many terms n does it have?
Sequences & series worksheet with answers
1.Easy
a₁ = −3d = −4aₙ = −39
n =
2.Easy
The geometric sequence aₙ = 5·0.6ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.01.
a₁ = 5r = 0.6ε = 0.01
n =
3.Medium
Exactly one of the four series converges. Click it.
A: Σ 3ᵏ/k²B: Σ 1/(3ᵏ + k)C: Σ (1 + 1/k)ᵏD: Σ 1/√k
- 1A: Σ 3ᵏ/k²
- 2B: Σ 1/(3ᵏ + k)
- 3C: Σ (1 + 1/k)ᵏ
- 4D: Σ 1/√k
4.Medium
Find the sum S = Σk=1∞ 3/(k(k + 3)).
ak = 3/(k(k + 3))
S =
5.Hard
f(x) = eˣ is approximated by its Maclaurin polynomial of degree 5 at x = 0.5. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = e0.5 = 1.649 to find the largest possible error |R₅|.
f(x) = eˣn = 5x = 0.5M = 1.649
|R₅| =
6.Hard
Use the Maclaurin polynomial of degree 4 of f(x) = 1/(1 − x) to approximate f(0.5). Give P₄(0.5).
f(x) = 1/(1 − x)n = 4x = 0.5
P₄(0.5) =
Answer key
- 1. n = 10
- 2. n = 14
- 3. B: Σ 1/(3ᵏ + k)
- 4. S = 1.833
- 5. |R₅| = 3.578 × 10⁻⁵
- 6. P₄(0.5) = 1.938
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