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Find a linear differential operator that annihilates the given function (use D for the differential operator) e^-x + 7xe^x - x^2 e^x
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Answer

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Step 1:
: Identify the given function

The given function is $f(x) = e^{-x} + 7xe^{x} - x^2 e^{x}$.

Step 2:
: Find the derivative of the function

\frac{df(x)}{dx} = -e^{-x} + 7e^{x} + 7xe^{x} - 2x e^{x}
In order to find a linear differential operator that annihilates the given function, we first need to find the derivative of the function.

Step 3:
: Factor out $e^{x}$

\frac{df(x)}{dx} = e^{x} (-1 + 7x - 2x^2 + 7 - x)

Step 4:
: Set the derivative equal to zero and solve for $x$

x = 1, 3
To find the annihilator, we need to find a linear differential operator that makes the derivative equal to zero. Rearranging the terms, we have: Dividing the entire equation by 2, we get: Factoring the quadratic equation, we get:

Step 5:
: Form the annihilator

(D - 1)(D - 3)
A linear differential operator that annihilates the given function is:

Final Answer

The annihilator for the given function $f(2$) = e^{-x} + 7xe^{x} - x^2 e^{x}$ is $(D - 1)(D - 3)$.