Find the sum S6 of the first 6 terms of the geometric sequence 5, 10, 20, …
Sequences & series worksheet with answers
1.Easy
a₁ = 5r = 2n = 6
S6 =
2.Easy
A ball is dropped and its first rebound reaches 3 m. Every next rebound reaches 85% of the previous one. Which rebound n is the first one lower than 0.5 m?
a₁ = 3r = 0.85ε = 0.5
n =
3.Medium
The power series Σk=1∞ (x − 3)ᵏ/(k²·2ᵏ) converges on an interval around x₀ = 3. Find the left end x of that interval.
Σ (x − 3)ᵏ/(k²·2ᵏ)x₀ = 3
x =
4.Medium
Find the sum S = Σk=1∞ 5/(k(k + 1)).
ak = 5/(k(k + 1))
S =
5.Hard
f(x) = cos x is approximated by its Maclaurin polynomial of degree 4 at x = 0.8. 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 = 0.8M = 1
|R₄| =
6.Hard
f(x) = sin x is approximated by its Maclaurin polynomial of degree 3 at x = 1. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 1 to find the largest possible error |R₃|.
f(x) = sin xn = 3x = 1M = 1
|R₃| =
Answer key
- 1. S6 = 315
- 2. n = 13
- 3. x = 1
- 4. S = 5
- 5. |R₄| = 0.002731
- 6. |R₃| = 0.04167
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