Maclaurin Series: Find a_n for f(x) = 1/(1+3x)

In summary, a Maclaurin series is an infinite series that represents a function as a sum of polynomials, centered at x=0 and a special case of a Taylor series. The coefficients (a_n) for a Maclaurin series can be found by taking the nth derivative of the function at x=0 and dividing it by n!, using the formula a_n = f^(n)(0)/n!. The Maclaurin series for f(x) = 1/(1+3x) is a_0 + a_1x + a_2x^2 + a_3x^3 + ..., where a_n = (-3)^n. The number of terms needed to get a good approximation
  • #1
Kuno
19
0

Homework Statement


find [tex]a_{n}[/tex] for [tex]f(x)\ =\ \frac{1}{1+3x}[/tex]

The Attempt at a Solution


I got:
f(0) = 1
f'(0) = -3
f''(0) = 9

The answer I ended up with was:
[tex]a_{n} \ = \ {(-1)}^n\frac{3^n}{n!}[/tex]

However, the answer in the back of my book has the same answer except it's not divided by n!.
 
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  • #2
the n! is canceled out somehow. Recheck your workings.

Hint: Find f^n(x). I don't know what's the notation for the nth derivative of f(x)
 
  • #3
Okay I see it now, thanks.
 
  • #4
you're welcome :)
 

What is a Maclaurin series?

A Maclaurin series is a type of infinite series that represents a function as a sum of polynomials. It is centered at x=0 and is a special case of a Taylor series.

How do you find the coefficients (a_n) for a Maclaurin series?

The coefficients (a_n) for a Maclaurin series can be found by taking the nth derivative of the function at x=0 and dividing it by n!. This can be simplified using the formula a_n = f^(n)(0)/n!.

What is the Maclaurin series for f(x) = 1/(1+3x)?

The Maclaurin series for f(x) = 1/(1+3x) is a_0 + a_1x + a_2x^2 + a_3x^3 + ..., where a_n = (-3)^n.

How many terms of the Maclaurin series do I need to use to get a good approximation of f(x) = 1/(1+3x)?

The number of terms needed to get a good approximation of f(x) = 1/(1+3x) depends on the desired level of precision. Generally, the more terms used, the more accurate the approximation will be.

What is the radius of convergence for the Maclaurin series of f(x) = 1/(1+3x)?

The radius of convergence for the Maclaurin series of f(x) = 1/(1+3x) is 1/3. This means that the series will converge for all x values within a radius of 1/3 from the center (x=0).

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