The arithmetic sequence 6, 10, 14, 18, … ends with the term 66. How many terms n does it have?
Sequences & series worksheet with answers
1.Easy
a₁ = 6d = 4aₙ = 66
n =
2.Easy
Find the sum S of the infinite series Σk=2∞ 9·(−2/3)ᵏ.
a = 9r = −2/3k₀ = 2
S =
3.Medium
Apply the ratio test to Σk=1∞ (k!)²·1ᵏ/(2k)!. Find L = lim |ak+1/ak|.
ak = (k!)²·1ᵏ/(2k)!
L =
4.Medium
Find the radius of convergence R of the power series Σk=1∞ 3ᵏ·xᵏ/(k + 1).
Σ 3ᵏ·xᵏ/(k + 1)x₀ = 0
R =
5.Hard
f(x) = cos x is approximated by its Maclaurin polynomial of degree 3 at x = 0.2. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 1 to find the largest possible error |R₃|.
f(x) = cos xn = 3x = 0.2M = 1
|R₃| =
6.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ·1.22k/(2k)!.
ak = (−1)ᵏ·1.22k/(2k)!
S =
Answer key
- 1. n = 16
- 2. S = 2.4
- 3. L = 0.25
- 4. R = 0.3333
- 5. |R₃| = 6.667 × 10⁻⁵
- 6. S = 0.3624
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