Derivative of 3e^-x

1. The derivative of a constant times a function is the constant times the derivative of the function.

   1. Let $u = - x$.

   2. The derivative of $e^{u}$ is itself.

   3. Then, apply the chain rule. Multiply by $\frac{d}{d x} \left(- x\right)$:

      1. The derivative of a constant times a function is the constant times the derivative of the function.

         1. Apply the power rule: $x$ goes to $1$

         So, the result is: $-1$

      The result of the chain rule is:

      $$- e^{- x}$$

   So, the result is: $- 3 e^{- x}$

The answer is:

$$- 3 e^{- x}$$