Find the sum S of the infinite series Σk=1∞ 5·(3/4)ᵏ.
Sequences & series worksheet with answers
1.Easy
a = 5r = 3/4k₀ = 1
S =
2.Easy
Find the sum S of the infinite series Σk=1∞ 6·(−2/3)ᵏ.
a = 6r = −2/3k₀ = 1
S =
3.Medium
Find the sum S = Σk=1∞ 1/(k(k + 3)).
ak = 1/(k(k + 3))
S =
4.Medium
Find the sum S = Σk=120 12/(k(k + 1)).
ak = 12/(k(k + 1))n = 20
S =
5.Hard
f(x) = eˣ is approximated at x = 0.5 by its Maclaurin polynomial of degree n. With the Lagrange bound M·|x|ⁿ⁺¹/(n + 1)! and M = 2, find the smallest degree n that guarantees an error below 0.001.
f(x) = eˣx = 0.5M = 2ε = 0.001
n =
6.Hard
f(x) = sin 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 = 1 to find the largest possible error |R₄|.
f(x) = sin xn = 4x = 0.2M = 1
|R₄| =
Answer key
- 1. S = 15
- 2. S = −2.4
- 3. S = 0.6111
- 4. S = 11.43
- 5. n = 4
- 6. |R₄| = 2.667 × 10⁻⁶
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