Find the sum S of the infinite series Σk=2∞ 5·(2/5)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 5r = 2/5k₀ = 2
S =
2.Easy
Find the sum S of the infinite series Σk=0∞ 5·(−3/4)ᵏ.
a = 5r = −3/4k₀ = 0
S =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ k²/5ᵏB: Σ 2/kC: Σ 1/(k(k + 1))D: Σ (3/4)ᵏ
- 1A: Σ k²/5ᵏ
- 2B: Σ 2/k
- 3C: Σ 1/(k(k + 1))
- 4D: Σ (3/4)ᵏ
4.Medium
Apply the ratio test to Σk=1∞ kᵏ/(2ᵏ·k!). Find L = lim |ak+1/ak|.
ak = kᵏ/(2ᵏ·k!)
L =
5.Hard
f(x) = cos x 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 = 1 to find the largest possible error |R₅|.
f(x) = cos xn = 5x = −0.5M = 1
|R₅| =
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. S = 1.333
- 2. S = 2.857
- 3. B: Σ 2/k
- 4. L = 1.359
- 5. |R₅| = 2.17 × 10⁻⁵
- 6. S = 0.2231
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