How do I find the MacLaurin series for $\frac{1}{1 - 2x}$?

In summary, to find the Maclaurin series of $\frac{1}{1-2x}$, you can use the known series for $\frac{1}{1-x}$ and plug in $2x$, keeping in mind that the series converges for $|x| < \frac{1}{2}$. This results in the series $\sum_{n=0}^\infty (2x)^n$, but it would be preferred to write it as $\sum_{n=0}^\infty c_n \, x^n$ to fit the Maclaurin series format.
  • #1
tmt1
234
0
I need to find the maclaurin series of the function

$$\frac{1}{1 - 2x}$$.

I know $\frac{1}{1 - x}$ is $1 + x + x^2 + x^3 ...$ but how can I use this to solve the problem? I don't think I can just plug in $2x$ can I?
 
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  • #2
Yes; plug in $2x$ and note that the series converges for $|x|<\dfrac12$.
 
  • #3
greg1313 said:
Yes; plug in $2x$ and note that the series converges for $|x|<\dfrac12$.

So, I would get something like

$$\sum_{n = 0}^{\infty} 2^nx^n$$

Is this correct?
 
  • #4
Yes, but I think the notation

$$\sum_{n=0}^\infty(2x)^n$$

would be preferred. :)
 
  • #5
greg1313 said:
Yes, but I think the notation

$$\sum_{n=0}^\infty(2x)^n$$

would be preferred. :)

Actually, as it's specifically asked to be written as a MacLaurin Series, where it should be written $\displaystyle \begin{align*} \sum_{n = 0}^{\infty}{c_n\,x^n} \end{align*}$ the OP's notation would be preferred.
 

1. What is a Maclaurin series?

A Maclaurin series is a type of power series expansion that represents a function as a sum of infinitely many terms. It is named after Scottish mathematician Colin Maclaurin.

2. Why do we use Maclaurin series?

Maclaurin series are useful in mathematics and science because they allow us to approximate complicated functions with simpler polynomial expressions. This can make it easier to solve problems or make predictions.

3. How do you find a Maclaurin series?

To find a Maclaurin series, we use a process called Taylor series expansion. This involves taking derivatives of a function at a specific point and plugging those values into a formula. The resulting expression is the Maclaurin series for the given function.

4. What is the difference between a Maclaurin series and a Taylor series?

A Maclaurin series is a special case of a Taylor series, where the expansion point is at 0. In other words, a Maclaurin series is a Taylor series that is centered at 0.

5. Can a Maclaurin series represent any function?

No, not all functions can be represented by a Maclaurin series. The function must be infinitely differentiable at the expansion point in order for a Maclaurin series to exist. However, many commonly used functions can be represented by Maclaurin series.

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