A1. The derivative of the function $f(x)=2 e^{-\frac{1}{2} x}$ is equal to
(A) $2 e^{\frac{1}{2} x}$
(B) $-2 e^{-\frac{1}{2} x}$
(C) $-e^{-\frac{1}{2} x}$
(D) $e^{-\frac{1}{2} x}$
(E) $2 \ln \left(-\frac{1}{2} x\right)$
A1. The derivative of this function is $f^{\prime}(x)=2 \cdot e^{-\frac{1}{2} x} \cdot\left(-\frac{1}{2}\right)=-e^{-\frac{1}{2} x}$.