Find the sum S5 of the first 5 terms of the geometric sequence 4, −12, 36, …
Sequences & series worksheet with answers
1.Easy
a₁ = 4r = −3n = 5
S5 =
2.Easy
Find the sum S of the infinite series Σk=1∞ 2·(−1/4)ᵏ.
a = 2r = −1/4k₀ = 1
S =
3.Medium
Find the radius of convergence R of the power series Σk=1∞ (x − 3)ᵏ/2ᵏ.
Σ (x − 3)ᵏ/2ᵏx₀ = 3
R =
4.Medium
Find the sum S = Σk=1∞ 6/(k(k + 4)).
ak = 6/(k(k + 4))
S =
5.Hard
f(x) = eˣ is approximated by its Maclaurin polynomial of degree 4 at x = −0.5. Use the Lagrange error bound M·|x|ⁿ⁺¹/(n + 1)! with M = 1 to find the largest possible error |R₄|.
f(x) = eˣn = 4x = −0.5M = 1
|R₄| =
6.Hard
Use the Maclaurin polynomial of degree 4 of f(x) = eˣ to approximate f(2.5). Give P₄(2.5).
f(x) = eˣn = 4x = 2.5
P₄(2.5) =
Answer key
- 1. S5 = 244
- 2. S = −0.4
- 3. R = 2
- 4. S = 3.125
- 5. |R₄| = 0.0002604
- 6. P₄(2.5) = 10.86
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