Find the sum S15 of the first 15 terms of the arithmetic sequence −10, −6, −2, 2, …
Sequences & series worksheet with answers
1.Easy
a₁ = −10d = 4n = 15
S15 =
2.Easy
A ball is dropped and its first rebound reaches 8 m. Every next rebound reaches 80% of the previous one. Which rebound n is the first one lower than 0.05 m?
a₁ = 8r = 0.8ε = 0.05
n =
3.Medium
Apply the ratio test to Σk=1∞ (k!)²·8ᵏ/(2k)!. Find L = lim |ak+1/ak|.
ak = (k!)²·8ᵏ/(2k)!
L =
4.Medium
Find the sum S = Σk=1∞ 1/(k(k + 2)).
ak = 1/(k(k + 2))
S =
5.Hard
f(x) = eˣ 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 = e0.8 = 2.226 to find the largest possible error |R₄|.
f(x) = eˣn = 4x = 0.8M = 2.226
|R₄| =
6.Hard
Find the coefficient c₂ of (x − 3)² in the Taylor series of f(x) = ln x about a = 3.
f(x) = ln xa = 3k = 2
c₂ =
Answer key
- 1. S15 = 270
- 2. n = 24
- 3. L = 2
- 4. S = 0.75
- 5. |R₄| = 0.006077
- 6. c₂ = −0.05556
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