The arithmetic sequence −10, −12, −14, −16, … ends with the term −32. How many terms n does it have?
Sequences & series worksheet with answers
1.Easy
a₁ = −10d = −2aₙ = −32
n =
2.Easy
The geometric sequence aₙ = 20·0.85ⁿ⁻¹ decreases. Find the first index n for which aₙ < 0.5.
a₁ = 20r = 0.85ε = 0.5
n =
3.Medium
Apply the root test to Σk=1∞ ((4k + 1)/(6k + 3))ᵏ. Find L = lim |ak|1/k.
ak = ((4k + 1)/(6k + 3))ᵏ
L =
4.Medium
Find the sum S = Σk=1∞ 6/(k(k + 4)).
ak = 6/(k(k + 4))
S =
5.Hard
f(x) = sin x 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 = 1 to find the largest possible error |R₄|.
f(x) = sin xn = 4x = 0.8M = 1
|R₄| =
6.Hard
Find the coefficient c₂ of (x − 16)² in the Taylor series of f(x) = √x about a = 16.
f(x) = √xa = 16k = 2
c₂ =
Answer key
- 1. n = 12
- 2. n = 24
- 3. L = 0.6667
- 4. S = 3.125
- 5. |R₄| = 0.002731
- 6. c₂ = −0.001953
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