Find the sum S7 of the first 7 terms of the geometric sequence 10, 30, 90, …
Sequences & series worksheet with answers
1.Easy
a₁ = 10r = 3n = 7
S7 =
2.Easy
Find the sum S9 of the first 9 terms of the arithmetic sequence 6, 12, 18, 24, …
a₁ = 6d = 6n = 9
S9 =
3.Medium
Find the sum S = Σk=1∞ 4/(k(k + 4)).
ak = 4/(k(k + 4))
S =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ (1 + 1/k)ᵏB: Σ (−1)ᵏ/kC: Σ k³/5ᵏD: Σ (2/3)ᵏ
- 1A: Σ (1 + 1/k)ᵏ
- 2B: Σ (−1)ᵏ/k
- 3C: Σ k³/5ᵏ
- 4D: Σ (2/3)ᵏ
5.Hard
f(x) = cos x is approximated by its Maclaurin polynomial of degree 4 at x = 1. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 1 to find the largest possible error |R₄|.
f(x) = cos xn = 4x = 1M = 1
|R₄| =
6.Hard
Recognise the series and find its sum: S = Σk=1∞ (−1)k+1·0.25ᵏ/k.
ak = (−1)k+1·0.25ᵏ/k
S =
Answer key
- 1. S7 = 10930
- 2. S9 = 270
- 3. S = 2.083
- 4. A: Σ (1 + 1/k)ᵏ
- 5. |R₄| = 0.008333
- 6. S = 0.2231
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