Find the sum S22 of the first 22 terms of the arithmetic sequence −12, −7, −2, 3, …
Sequences & series worksheet with answers
1.Easy
a₁ = −12d = 5n = 22
S22 =
2.Easy
Find the sum S of the infinite series Σk=2∞ 12·(4/5)ᵏ.
a = 12r = 4/5k₀ = 2
S =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ 1/kB: Σ (1/2)ᵏC: Σ 3ᵏ/k!D: Σ 1/(k² + 4)
- 1A: Σ 1/k
- 2B: Σ (1/2)ᵏ
- 3C: Σ 3ᵏ/k!
- 4D: Σ 1/(k² + 4)
4.Medium
Find the radius of convergence R of the power series Σk=1∞ 25ᵏx²ᵏ/k.
Σ 25ᵏx²ᵏ/kx₀ = 0
R =
5.Hard
Recognise the series and find its sum: S = Σk=1∞ (−1)k+1·0.5ᵏ/k.
ak = (−1)k+1·0.5ᵏ/k
S =
6.Hard
f(x) = cos x is approximated by its Maclaurin polynomial of degree 4 at x = −0.5. 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 = −0.5M = 1
|R₄| =
Answer key
- 1. S22 = 891
- 2. S = 38.4
- 3. A: Σ 1/k
- 4. R = 0.2
- 5. S = 0.4055
- 6. |R₄| = 0.0002604
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