Find the sum S9 of the first 9 terms of the geometric sequence 2, 1.6, 1.28, …
Sequences & series worksheet with answers
1.Easy
a₁ = 2r = 0.8n = 9
S9 =
2.Easy
Find the sum S5 of the first 5 terms of the geometric sequence 10, −5, 2.5, …
a₁ = 10r = −0.5n = 5
S5 =
3.Medium
Apply the ratio test to Σk=1∞ k³·3ᵏ/5ᵏ. Find L = lim |ak+1/ak|.
ak = k³·3ᵏ/5ᵏ
L =
4.Medium
Exactly one of the four series converges. Click it.
A: Σ (k + 1)/k²B: Σ 3ᵏ/k²C: Σ 2/kD: Σ 1/(k² + 3)
- 1A: Σ (k + 1)/k²
- 2B: Σ 3ᵏ/k²
- 3C: Σ 2/k
- 4D: Σ 1/(k² + 3)
5.Hard
Use the Maclaurin polynomial of degree 4 of f(x) = 1/(1 + x) to approximate f(0.5). Give P₄(0.5).
f(x) = 1/(1 + x)n = 4x = 0.5
P₄(0.5) =
6.Hard
f(x) = eˣ is approximated by its Maclaurin polynomial of degree 2 at x = 0.8. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = e0.8 = 2.226 to find the largest possible error |R₂|.
f(x) = eˣn = 2x = 0.8M = 2.226
|R₂| =
Answer key
- 1. S9 = 8.658
- 2. S5 = 6.875
- 3. L = 0.6
- 4. D: Σ 1/(k² + 3)
- 5. P₄(0.5) = 0.6875
- 6. |R₂| = 0.1899
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