- #1
Fernando Rios
- 96
- 10
- Homework Statement
- Find the interval of convergence of each of the following power series; be sure to investigate
the endpoints of the interval in each case.
- Relevant Equations
- ∑(x^(2n)/((2^n)(n^2)))
∑(x2n/(2nn2))
We use the ratio test:
ρn = |(x2n2/(2(n+1)2)|
ρ = |x2/2|
ρ < 1
|x2| < 2
|x| = √(2)
We investigate the endpoints:
x = 2:
∑(4n/(2nn2) = ∑(2n/n2))
We use the preliminary test:
limn→∞ 2n/n2 = ∞
Since the numerator is greater than the denominator. Therefore, x = 2 shouldn't be included. However, then answer says it should be included.
We use the ratio test:
ρn = |(x2n2/(2(n+1)2)|
ρ = |x2/2|
ρ < 1
|x2| < 2
|x| = √(2)
We investigate the endpoints:
x = 2:
∑(4n/(2nn2) = ∑(2n/n2))
We use the preliminary test:
limn→∞ 2n/n2 = ∞
Since the numerator is greater than the denominator. Therefore, x = 2 shouldn't be included. However, then answer says it should be included.
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