Find the sum S of the infinite series Σk=1∞ 12·(4/5)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 12r = 4/5k₀ = 1
S =
2.Easy
Find the term a20 of the arithmetic sequence −9, −7, −5, −3, …
a₁ = −9d = 2n = 20
a20 =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ (3/4)ᵏB: Σ 1/k²C: Σ (5/4)ᵏD: Σ 1/(3ᵏ + k)
- 1A: Σ (3/4)ᵏ
- 2B: Σ 1/k²
- 3C: Σ (5/4)ᵏ
- 4D: Σ 1/(3ᵏ + k)
4.Medium
Find the sum S = Σk=1∞ 1/(k(k + 4)).
ak = 1/(k(k + 4))
S =
5.Hard
Recognise the series and find its sum: S = Σk=0∞ 2ᵏ/k!.
ak = 2ᵏ/k!
S =
6.Hard
f(x) = ln(1 + x) is approximated by its Maclaurin polynomial of degree 3 at x = 0.2. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 3! = 6 to find the largest possible error |R₃|.
f(x) = ln(1 + x)n = 3x = 0.2M = 6
|R₃| =
Answer key
- 1. S = 48
- 2. a20 = 29
- 3. C: Σ (5/4)ᵏ
- 4. S = 0.5208
- 5. S = 7.389
- 6. |R₃| = 0.0004
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