Question

What is the derivative of e to the poker minus x

Answer 1

Y = $e^{-x}$                

let u = x

y = $e^{u}$

dy/dx = dy/du  * du/dx

dy/du =  $e^{u}$

du/dx = -1

dy/dx =  $e^{u}$  * -1

dy/dx =  -$e^{u}$

dy/dx = -$e^{-x}$   

Answer 2

$(e^{-x})'=e^{-x}\cdot(-x)'=e^{-x}\cdot(-1)=-e^{-x}$