Power series expansion of an exponential

In summary, the conversation was about how to expand the exponential term in the equation y=2[e^{x+(x²/2)}-1] as a power series. The solution was found by substituting x+(x²/2) as "x" in the given formula and proceeding as normal. The resulting power series was y=2x+2x²+(x^3)+(x^4)/4. However, there may have been a mistake made as the previously worked solution of y=2x+x²+c and the original equation y=2[e^{x+(x²/2)}-1] only agreed up to the first power of x. The question asking to show this agreement up to the power
  • #1
t_n_p
595
0

Homework Statement



expand the exponential term in the equation y=2[e^{x+(x²/2)}-1] as a power series

Homework Equations



on wikipedia I found this...
http://img297.imageshack.us/img297/1088/15139862vw6.jpg

The Attempt at a Solution


Do I substitute x+(x²/2) as "x" in the above formula and proceed as normal or must I do something different?
 
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  • #2
t_n_p said:

Homework Statement



The Attempt at a Solution


Do I substitute x+(x²/2) as "x" in the above formula and proceed as normal or must I do something different?

Yes, just substitute.
 
  • #3
Don't forget to multiply each term by 2 and subtract 1 from the constant term.
 
  • #4
HallsofIvy said:
Don't forget to multiply each term by 2 and subtract 1 from the constant term.

And brush your teeth! :biggrin:
 
  • #5
Thanks for the quick replies.
Using "x" = x+x²/2

I get y=2{1 + x + x²/2 + (x+x²/2)²/2 +...}-1
this leads to..

y=2x+2x²+(x^3)+(x^4)/4

I think I may have made a mistake but I cannot see where. My reason being I am supposed to show that a previously worked solution of y=2x+x²+c and the original equation y=2[e^{x+(x²/2)}-1] agree up to the first power of x only.

firstly, in the previously worked solution i am missing a coefficient of 2 for x². Secondly, why would the question ask to show that the original solution only agrees with the power series expansion of the same equation only to the power of x? It makes no sense!
 
  • #6
I suggest you post the relevant question here. We can't figure out what's wrong unless we know what the question asks.
 

1. What is a power series expansion of an exponential?

A power series expansion of an exponential is a mathematical representation of an exponential function as an infinite sum of powers of its variable. It is often used to approximate or evaluate the exponential function for values outside of its defined domain.

2. How is a power series expansion of an exponential calculated?

A power series expansion of an exponential is calculated by using the Taylor series method, which involves taking derivatives of the exponential function at a chosen point and plugging them into the general formula for a Taylor series.

3. What is the significance of a power series expansion of an exponential in mathematical analysis?

The power series expansion of an exponential is significant in mathematical analysis because it allows for the evaluation of complicated functions by breaking them down into simpler components. It also helps in understanding the behavior of a function and making predictions about its values.

4. How accurate is a power series expansion of an exponential?

The accuracy of a power series expansion of an exponential depends on the number of terms included in the series. The more terms included, the closer the approximation will be to the actual value. However, for some values of the variable, the series may not converge, leading to a less accurate approximation.

5. Are there any real-world applications of power series expansions of exponential functions?

Yes, power series expansions of exponential functions have various real-world applications in fields such as engineering, physics, and finance. They are used to model and predict the behavior of physical systems, calculate interest rates and compound growth, and approximate solutions to differential equations.

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