Find the Taylor series at $x=0$ of the given function. Use suitable operations (differentiation, substitution, etc.) on the Taylor series at $x=0$ of $\frac{1}{1-x}, e^{x},$ or $\cos x .$ These series are derived in Examples 1 and 2 and Check Your Understanding Problem 2.
$$3\left(e^{-2 x}-2\right)$$