Find the sum S10 of the first 10 terms of the geometric sequence 10, −30, 90, …
Sequences & series worksheet with answers
1.Easy
a₁ = 10r = −3n = 10
S10 =
2.Easy
The arithmetic sequence −2, 0.5, 3, 5.5, … ends with the term 68. How many terms n does it have?
a₁ = −2d = 2.5aₙ = 68
n =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ 2/k²B: Σ (−1)ᵏ/kC: Σ k/5ᵏD: Σ ln k / k
- 1A: Σ 2/k²
- 2B: Σ (−1)ᵏ/k
- 3C: Σ k/5ᵏ
- 4D: Σ ln k / k
4.Medium
Exactly one of the four series converges. Click it.
A: Σ (4/3)ᵏB: Σ 1/√kC: Σ (3k + 1)/(k + 2)D: Σ 10ᵏ/k!
- 1A: Σ (4/3)ᵏ
- 2B: Σ 1/√k
- 3C: Σ (3k + 1)/(k + 2)
- 4D: Σ 10ᵏ/k!
5.Hard
f(x) = cos x is approximated by its Maclaurin polynomial of degree 3 at x = −0.5. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 1 to find the largest possible error |R₃|.
f(x) = cos xn = 3x = −0.5M = 1
|R₃| =
6.Hard
Use the Maclaurin polynomial of degree 4 of f(x) = cos(3x) to approximate f(0.5). Give P₄(0.5).
f(x) = cos(3x)n = 4x = 0.5
P₄(0.5) =
Answer key
- 1. S10 = −147620
- 2. n = 29
- 3. D: Σ ln k / k
- 4. D: Σ 10ᵏ/k!
- 5. |R₃| = 0.002604
- 6. P₄(0.5) = 0.08594
Full step-by-step solutions: practise this topic on examproblems.com.