The arithmetic sequence 10, 7, 4, 1, … ends with the term −83. How many terms n does it have?
Sequences & series worksheet with answers
1.Easy
a₁ = 10d = −3aₙ = −83
n =
2.Easy
Find the sum S9 of the first 9 terms of the geometric sequence 2, −4, 8, …
a₁ = 2r = −2n = 9
S9 =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ 1/(2ᵏ + k)B: Σ 3/kC: Σ 3/k³D: Σ (−1)ᵏ/√k
- 1A: Σ 1/(2ᵏ + k)
- 2B: Σ 3/k
- 3C: Σ 3/k³
- 4D: Σ (−1)ᵏ/√k
4.Medium
Find the sum S = Σk=1∞ 4/(k(k + 3)).
ak = 4/(k(k + 3))
S =
5.Hard
Find the coefficient c₂ of (x − 2)² in the Taylor series of f(x) = 1/x about a = 2.
f(x) = 1/xa = 2k = 2
c₂ =
6.Hard
f(x) = cos 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) = cos xx = 1M = 1ε = 1 × 10⁻⁶
n =
Answer key
- 1. n = 32
- 2. S9 = 342
- 3. B: Σ 3/k
- 4. S = 2.444
- 5. c₂ = 0.125
- 6. n = 9
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