Find the term a31 of the arithmetic sequence 1, 5, 9, 13, …
Sequences & series worksheet with answers
1.Easy
a₁ = 1d = 4n = 31
a31 =
2.Easy
Find the sum S11 of the first 11 terms of the arithmetic sequence −5, 0, 5, 10, …
a₁ = −5d = 5n = 11
S11 =
3.Medium
Apply the root test to Σk=1∞ ((2k + 2)/(4k + 6))ᵏ. Find L = lim |ak|1/k.
ak = ((2k + 2)/(4k + 6))ᵏ
L =
4.Medium
Apply the ratio test to Σk=1∞ (k!)²·3ᵏ/(2k)!. Find L = lim |ak+1/ak|.
ak = (k!)²·3ᵏ/(2k)!
L =
5.Hard
f(x) = cos x is approximated by its Maclaurin polynomial of degree 3 at x = 1. 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 = 1M = 1
|R₃| =
6.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ·1.52k+1/(2k + 1)!.
ak = (−1)ᵏ·1.52k+1/(2k + 1)!
S =
Answer key
- 1. a31 = 121
- 2. S11 = 220
- 3. L = 0.5
- 4. L = 0.75
- 5. |R₃| = 0.04167
- 6. S = 0.9975
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