Find the sum S7 of the first 7 terms of the geometric sequence 3, 6, 12, …
Sequences & series worksheet with answers
1.Easy
a₁ = 3r = 2n = 7
S7 =
2.Easy
Find the sum S5 of the first 5 terms of the geometric sequence 5, 2.5, 1.25, …
a₁ = 5r = 0.5n = 5
S5 =
3.Medium
Apply the ratio test to Σk=1∞ (k!)²·3ᵏ/(2k)!. Find L = lim |ak+1/ak|.
ak = (k!)²·3ᵏ/(2k)!
L =
4.Medium
Exactly one of the four series diverges. Click it.
A: Σ 1/(k(k + 4))B: Σ (−1)ᵏ/√kC: Σ (2/3)ᵏD: Σ 1/(4k + 6)
- 1A: Σ 1/(k(k + 4))
- 2B: Σ (−1)ᵏ/√k
- 3C: Σ (2/3)ᵏ
- 4D: Σ 1/(4k + 6)
5.Hard
Recognise the series and find its sum: S = Σk=0∞ (−1)ᵏ/(2k)!.
ak = (−1)ᵏ/(2k)!
S =
6.Hard
Use the Maclaurin polynomial of degree 4 of f(x) = cos(−x) to approximate f(2). Give P₄(2).
f(x) = cos(−x)n = 4x = 2
P₄(2) =
Answer key
- 1. S7 = 381
- 2. S5 = 9.688
- 3. L = 0.75
- 4. D: Σ 1/(4k + 6)
- 5. S = 0.5403
- 6. P₄(2) = −0.3333
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