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# Differentiation : Radius of Convergence for Power Series

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Consider the differnetial equation
y'(x) + xy(x) = 0 with y(0) = 0

Look for a solution of this problem of the form
y(x) = A + B + Ce^-x + De^-1/2x^2

Use the fact that y must satisfy the equation and the initial conditions to identify the constants A,B,C and D. By setting u = -x^2/2 in the power series for f(u) = exp{u}, determine a power series for y(x). What is the radius of convergence of the power series for y(x)?

I am having trouble in grasping the whole concept of this problem. Can anyone help?

##### Solution Summary

A radius of convergence for a power series is found. The solution is detailed and well-presented.

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Consider the differnetial equation
y'(x) + xy(x) = 0 with y(0) = 0

Look for a solution of this problem of the form

Use the fact that y must satisfy the equation and the initial conditions to indentify the constants A,B,C and D. By setting u = -x^2/2 in the power series for
f(u) = exp{u}, determine a power series for y(x). What is the ...

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###### Education
• BSc , Wuhan Univ. China
• MA, Shandong Univ.
###### Recent Feedback
• "Your solution, looks excellent. I recognize things from previous chapters. I have seen the standard deviation formula you used to get 5.154. I do understand the Central Limit Theorem needs the sample size (n) to be greater than 30, we have 100. I do understand the sample mean(s) of the population will follow a normal distribution, and that CLT states the sample mean of population is the population (mean), we have 143.74. But when and WHY do we use the standard deviation formula where you got 5.154. WHEN & Why use standard deviation of the sample mean. I don't understand, why don't we simply use the "100" I understand that standard deviation is the square root of variance. I do understand that the variance is the square of the differences of each sample data value minus the mean. But somehow, why not use 100, why use standard deviation of sample mean? Please help explain."
• "excellent work"
• "Thank you so much for all of your help!!! I will be posting another assignment. Please let me know (once posted), if the credits I'm offering is enough or you ! Thanks again!"
• "Thank you"
• "Thank you very much for your valuable time and assistance!"

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