The arithmetic sequence 15, 21, 27, 33, … ends with the term 171. How many terms n does it have?
Sequences & series worksheet with answers
1.Easy
a₁ = 15d = 6aₙ = 171
n =
2.Easy
The arithmetic sequence 15, 17.5, 20, 22.5, … ends with the term 100. How many terms n does it have?
a₁ = 15d = 2.5aₙ = 100
n =
3.Medium
Apply the root test to Σk=1∞ ((3k + 2)/(2k + 1))ᵏ. Find L = lim |ak|1/k.
ak = ((3k + 2)/(2k + 1))ᵏ
L =
4.Medium
Apply the ratio test to Σk=1∞ (k!)²·2ᵏ/(2k)!. Find L = lim |ak+1/ak|.
ak = (k!)²·2ᵏ/(2k)!
L =
5.Hard
Use the Maclaurin polynomial of degree 2 of f(x) = cos(3x) to approximate f(0.4). Give P₂(0.4).
f(x) = cos(3x)n = 2x = 0.4
P₂(0.4) =
6.Hard
Find the coefficient c₂ of (x − 4)² in the Taylor series of f(x) = ln x about a = 4.
f(x) = ln xa = 4k = 2
c₂ =
Answer key
- 1. n = 27
- 2. n = 35
- 3. L = 1.5
- 4. L = 0.5
- 5. P₂(0.4) = 0.28
- 6. c₂ = −0.03125
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