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Question
Math
Posted 5 months ago
a. Find the first four nonzero terms of the Maclaurin series for the given function.
b. Write the power series using summation notation.
c. Determine the interval of convergence of the series.
f(x)=5e5x
f(x)=5 e^{-5 x}
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Answer from Sia
Posted 5 months ago
Solution by Steps
step 1
To find the first four nonzero terms of the Maclaurin series for f(x)=5e5x f(x) = 5e^{-5x} , we will use the Maclaurin series expansion for ex e^x , which is ex=n=0xnn! e^x = \sum_{n=0}^{\infty} \frac{x^n}{n!}
step 2
Substituting 5x -5x for x x in the series expansion, we get e5x=n=0(5x)nn! e^{-5x} = \sum_{n=0}^{\infty} \frac{(-5x)^n}{n!}
step 3
Multiplying the series by 5, we obtain the series for 5e5x 5e^{-5x} : 5e5x=5n=0(5x)nn! 5e^{-5x} = 5 \sum_{n=0}^{\infty} \frac{(-5x)^n}{n!}
step 4
The first four nonzero terms of the series are given by the terms for n=0,1,2,3 n = 0, 1, 2, 3 : 5,25x,125x22!,625x33! 5, -25x, \frac{125x^2}{2!}, -\frac{625x^3}{3!}
Answer
The first four nonzero terms of the Maclaurin series for f(x)=5e5x f(x) = 5e^{-5x} are 5,25x,125x22,625x36 5, -25x, \frac{125x^2}{2}, -\frac{625x^3}{6} .
Key Concept
Maclaurin Series Expansion
Explanation
The Maclaurin series is a special case of the Taylor series centered at x=0 x = 0 . For the exponential function ex e^x , the series expansion is ex=n=0xnn! e^x = \sum_{n=0}^{\infty} \frac{x^n}{n!} . By substituting 5x -5x into this formula and multiplying by 5, we obtain the series for 5e5x 5e^{-5x} .


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step 1
To represent 5e5x 5e^{-5x} as a power series using summation notation, we start with the general form of the Maclaurin series for ex e^x : ex=n=0xnn! e^x = \sum_{n=0}^{\infty} \frac{x^n}{n!}
step 2
We substitute 5x -5x for x x to get the series for e5x e^{-5x} : e5x=n=0(5x)nn! e^{-5x} = \sum_{n=0}^{\infty} \frac{(-5x)^n}{n!}
step 3
Multiplying the series by 5 gives us the power series for 5e5x 5e^{-5x} : 5e5x=5n=0(5x)nn! 5e^{-5x} = 5 \sum_{n=0}^{\infty} \frac{(-5x)^n}{n!}
Answer
The power series for f(x)=5e5x f(x) = 5e^{-5x} using summation notation is 5n=0(5x)nn! 5 \sum_{n=0}^{\infty} \frac{(-5x)^n}{n!} .
Key Concept
Power Series Representation
Explanation
A power series is an infinite series of the form n=0an(xc)n \sum_{n=0}^{\infty} a_n(x - c)^n , where an a_n are the coefficients and c c is the center of the series. For 5e5x 5e^{-5x} , the power series is centered at x=0 x = 0 and has coefficients derived from the Maclaurin series expansion of ex e^x .


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step 1
To find the interval of convergence for the power series of 5e5x 5e^{-5x} , we can use the ratio test, which states that a series an \sum a_n converges if limnan+1an<1 \lim_{n \to \infty} \left| \frac{a_{n+1}}{a_n} \right| < 1
step 2
Applying the ratio test to the series n=0(5x)nn! \sum_{n=0}^{\infty} \frac{(-5x)^n}{n!} , we get limn(5x)n+1/(n+1)!(5x)n/n!=limn5xn+1 \lim_{n \to \infty} \left| \frac{(-5x)^{n+1}/(n+1)!}{(-5x)^n/n!} \right| = \lim_{n \to \infty} \left| \frac{-5x}{n+1} \right|
step 3
Since limn5xn+1=0 \lim_{n \to \infty} \left| \frac{-5x}{n+1} \right| = 0 for all x x , the ratio is less than 1 for all x x
step 4
Therefore, the interval of convergence for the power series of 5e5x 5e^{-5x} is all real numbers, (,) (-\infty, \infty)
Answer
The interval of convergence for the power series of f(x)=5e5x f(x) = 5e^{-5x} is (,) (-\infty, \infty) .
Key Concept
Interval of Convergence
Explanation
The interval of convergence for a power series is the set of all x x values for which the series converges. The exponential function ex e^x has a power series that converges for all x x , and thus the power series for 5e5x 5e^{-5x} also converges for all x x .

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