Determine the radius of convergence of the power series∞Xn=0−√2nx2n
Question
Determine the radius of convergence of the power series∞Xn=0−√2nx2n
Solution
To determine the radius of convergence of the power series, we can use the Ratio Test. The Ratio Test states that if the limit as n approaches infinity of the absolute value of the ratio of the (n+1)th term to the nth term of a series is less than 1, the series converges. If the limit is greater than 1, the series diverges. If the limit equals 1, the test is inconclusive.
The given power series is ∑ from n=0 to ∞ of (-√2)^n * x^(2n).
Let's denote a_n = (-√2)^n * x^(2n). Then a_(n+1) = (-√2)^(n+1) * x^(2(n+1)).
We want to find the limit as n approaches infinity of |a_(n+1) / a_n|.
This simplifies to |(-√2 * x^2)|.
We want this to be less than 1 for the series to converge.
So, | -√2 * x^2 | < 1.
Solving this inequality gives -1/√2 < x^2 < 1/√2.
Taking the square root of all parts of the inequality gives -1/√(2) < x < 1/√(2).
Therefore, the radius of convergence of the power series is 1/√(2).
Similar Questions
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