Find the sum S9 of the first 9 terms of the geometric sequence 4, −12, 36, …
Sequences & series worksheet with answers
1.Easy
a₁ = 4r = −3n = 9
S9 =
2.Easy
The arithmetic sequence 18, 22, 26, 30, … ends with the term 146. How many terms n does it have?
a₁ = 18d = 4aₙ = 146
n =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ 5ᵏ/k!B: Σ (−1)ᵏ/kC: Σ k!/10ᵏD: Σ 2/k⁴
- 1A: Σ 5ᵏ/k!
- 2B: Σ (−1)ᵏ/k
- 3C: Σ k!/10ᵏ
- 4D: Σ 2/k⁴
4.Medium
Apply the ratio test to Σk=1∞ (k!)²·1ᵏ/(2k)!. Find L = lim |ak+1/ak|.
ak = (k!)²·1ᵏ/(2k)!
L =
5.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ·0.52k+1/(2k + 1)!.
ak = (−1)ᵏ·0.52k+1/(2k + 1)!
S =
6.Hard
f(x) = ln(1 + x) is approximated by its Maclaurin polynomial of degree 4 at x = 0.2. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 4! = 24 to find the largest possible error |R₄|.
f(x) = ln(1 + x)n = 4x = 0.2M = 24
|R₄| =
Answer key
- 1. S9 = 19684
- 2. n = 33
- 3. C: Σ k!/10ᵏ
- 4. L = 0.25
- 5. S = 0.4794
- 6. |R₄| = 6.4 × 10⁻⁵
Full step-by-step solutions: practise this topic on examproblems.com.