Find the sum S18 of the first 18 terms of the arithmetic sequence −10, −12, −14, −16, …
Sequences & series worksheet with answers
1.Easy
a₁ = −10d = −2n = 18
S18 =
2.Easy
Find the sum S7 of the first 7 terms of the geometric sequence 0.5, 1, 2, …
a₁ = 0.5r = 2n = 7
S7 =
3.Medium
Exactly one of the four series converges. Click it.
A: Σ ln k / kB: Σ k³/5ᵏC: Σ 3ᵏ/k²D: Σ k/(k + 1)
- 1A: Σ ln k / k
- 2B: Σ k³/5ᵏ
- 3C: Σ 3ᵏ/k²
- 4D: Σ k/(k + 1)
4.Medium
Apply the root test to Σk=1∞ ((4k + 5)/(5k + 3))ᵏ. Find L = lim |ak|1/k.
ak = ((4k + 5)/(5k + 3))ᵏ
L =
5.Hard
f(x) = ln(1 + x) is approximated by its Maclaurin polynomial of degree 4 at x = 0.3. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 4! = 24 to find the largest possible error |R₄|.
f(x) = ln(1 + x)n = 4x = 0.3M = 24
|R₄| =
6.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ·0.82k+1/(2k + 1)!.
ak = (−1)ᵏ·0.82k+1/(2k + 1)!
S =
Answer key
- 1. S18 = −486
- 2. S7 = 63.5
- 3. B: Σ k³/5ᵏ
- 4. L = 0.8
- 5. |R₄| = 0.000486
- 6. S = 0.7174
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