# An Interesting Differential Equation

Calculus Level 3

Here is a differential equation:

$$x-2 = \frac{x^3}{e^x} \frac{df}{dx}$$

Given that $$f(1) = e$$, $$f(3)$$ is of the form $$\frac{e^a}{b}$$.

What is 2a+b?

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