Find the sum S9 of the first 9 terms of the geometric sequence 10, −5, 2.5, …
Sequences & series worksheet with answers
1.Easy
a₁ = 10r = −0.5n = 9
S9 =
2.Easy
A ball is dropped and its first rebound reaches 10 m. Every next rebound reaches 90% of the previous one. Which rebound n is the first one lower than 0.1 m?
a₁ = 10r = 0.9ε = 0.1
n =
3.Medium
Exactly one of the four series diverges. Click it.
A: Σ 1/(k² + 8)B: Σ (−1)ᵏ/kC: Σ 5ᵏ/k!D: Σ (5/3)ᵏ
- 1A: Σ 1/(k² + 8)
- 2B: Σ (−1)ᵏ/k
- 3C: Σ 5ᵏ/k!
- 4D: Σ (5/3)ᵏ
4.Medium
Apply the ratio test to Σk=1∞ k·5ᵏ/3ᵏ. Find L = lim |ak+1/ak|.
ak = k·5ᵏ/3ᵏ
L =
5.Hard
Find the coefficient c₃ of (x − 4)³ in the Taylor series of f(x) = ln x about a = 4.
f(x) = ln xa = 4k = 3
c₃ =
6.Hard
Use the Maclaurin polynomial of degree 3 of f(x) = sin(2x) to approximate f(0.8). Give P₃(0.8).
f(x) = sin(2x)n = 3x = 0.8
P₃(0.8) =
Answer key
- 1. S9 = 6.68
- 2. n = 45
- 3. D: Σ (5/3)ᵏ
- 4. L = 1.667
- 5. c₃ = 0.005208
- 6. P₃(0.8) = 0.9173
Full step-by-step solutions: practise this topic on examproblems.com.