Find the term a20 of the arithmetic sequence −3, −7, −11, −15, …
Sequences & series worksheet with answers
1.Easy
a₁ = −3d = −4n = 20
a20 =
2.Easy
Find the sum S5 of the first 5 terms of the geometric sequence 10, 8, 6.4, …
a₁ = 10r = 0.8n = 5
S5 =
3.Medium
Find the radius of convergence R of the power series Σk=1∞ 2ᵏ·(x − 3)ᵏ/(k + 1).
Σ 2ᵏ·(x − 3)ᵏ/(k + 1)x₀ = 3
R =
4.Medium
Apply the ratio test to Σk=1∞ k·3ᵏ/4ᵏ. Find L = lim |ak+1/ak|.
ak = k·3ᵏ/4ᵏ
L =
5.Hard
Use the Maclaurin polynomial of degree 3 of f(x) = ln(1 + x) to approximate f(0.5). Give P₃(0.5).
f(x) = ln(1 + x)n = 3x = 0.5
P₃(0.5) =
6.Hard
Find the coefficient c₂ of (x − 9)² in the Taylor series of f(x) = √x about a = 9.
f(x) = √xa = 9k = 2
c₂ =
Answer key
- 1. a20 = −79
- 2. S5 = 33.62
- 3. R = 0.5
- 4. L = 0.75
- 5. P₃(0.5) = 0.4167
- 6. c₂ = −0.00463
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