Math  /  Calculus

QuestionFind the Taylor polynomial T3(x)T_{3}(x) for the function ff centered at the number aa. f(x)=xe7x,a=0T3(x)=\begin{array}{r} f(x)=x e^{-7 x}, \quad a=0 \\ T_{3}(x)=\square \end{array}
Graph ff and T3T_{3} in the same viewing rectangle.

Studdy Solution

STEP 1

1. We are finding the Taylor polynomial of degree 3 for the function f(x)=xe7x f(x) = x e^{-7x} .
2. The Taylor polynomial is centered at a=0 a = 0 .
3. The Taylor polynomial T3(x) T_3(x) approximates f(x) f(x) around x=0 x = 0 .

STEP 2

1. Calculate the necessary derivatives of f(x) f(x) .
2. Evaluate these derivatives at x=a=0 x = a = 0 .
3. Construct the Taylor polynomial T3(x) T_3(x) .
4. Graph the function f(x) f(x) and the polynomial T3(x) T_3(x) .

STEP 3

Calculate the first derivative of f(x)=xe7x f(x) = x e^{-7x} .
f(x)=e7x7xe7x f'(x) = e^{-7x} - 7xe^{-7x}

STEP 4

Calculate the second derivative of f(x) f(x) .
f(x)=14e7x+49xe7x f''(x) = -14e^{-7x} + 49xe^{-7x}

STEP 5

Calculate the third derivative of f(x) f(x) .
f(x)=98e7x343xe7x f'''(x) = 98e^{-7x} - 343xe^{-7x}

STEP 6

Evaluate f(x) f(x) and its derivatives at x=0 x = 0 .
f(0)=0e0=0f(0) = 0 \cdot e^{0} = 0
f(0)=e070e0=1f'(0) = e^{0} - 7 \cdot 0 \cdot e^{0} = 1
f(0)=14e0+490e0=14f''(0) = -14 \cdot e^{0} + 49 \cdot 0 \cdot e^{0} = -14
f(0)=98e03430e0=98f'''(0) = 98 \cdot e^{0} - 343 \cdot 0 \cdot e^{0} = 98

STEP 7

Construct the Taylor polynomial T3(x) T_3(x) using the formula:
\[ T_3(x) = f(0) + f'(0)x + \frac{f''(0)}{2!}x^2 + \frac{f'''(0)}{3!}x^3 $
Substituting the evaluated derivatives:
\[ T_3(x) = 0 + 1 \cdot x + \frac{-14}{2}x^2 + \frac{98}{6}x^3 $
Simplifying:
\[ T_3(x) = x - 7x^2 + \frac{49}{3}x^3 $

STEP 8

Graph f(x)=xe7x f(x) = x e^{-7x} and T3(x)=x7x2+493x3 T_3(x) = x - 7x^2 + \frac{49}{3}x^3 in the same viewing rectangle.
The Taylor polynomial T3(x) T_3(x) is:
x7x2+493x3 \boxed{x - 7x^2 + \frac{49}{3}x^3}

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