The arithmetic sequence −5, −1, 3, 7, … ends with the term 67. How many terms n does it have?
Sequences & series worksheet with answers
1.Easy
a₁ = −5d = 4aₙ = 67
n =
2.Easy
The arithmetic sequence 8, 14, 20, 26, … ends with the term 170. How many terms n does it have?
a₁ = 8d = 6aₙ = 170
n =
3.Medium
Find the sum S = Σk=1∞ 12/(k(k + 4)).
ak = 12/(k(k + 4))
S =
4.Medium
Apply the ratio test to Σk=1∞ k³·3ᵏ/4ᵏ. Find L = lim |ak+1/ak|.
ak = k³·3ᵏ/4ᵏ
L =
5.Hard
f(x) = cos x is approximated at x = 1.5 by its Maclaurin polynomial of degree n. With the Lagrange bound M·|x|ⁿ⁺¹/(n + 1)! and M = 1, find the smallest degree n that guarantees an error below 0.001.
f(x) = cos xx = 1.5M = 1ε = 0.001
n =
6.Hard
f(x) = cos x is approximated at x = 1.5 by its Maclaurin polynomial of degree n. With the Lagrange bound M·|x|ⁿ⁺¹/(n + 1)! and M = 1, find the smallest degree n that guarantees an error below 0.0005.
f(x) = cos xx = 1.5M = 1ε = 0.0005
n =
Answer key
- 1. n = 19
- 2. n = 28
- 3. S = 6.25
- 4. L = 0.75
- 5. n = 7
- 6. n = 8
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