Question

Find \frac{dy}{dx} and \frac{d^2y}{dx^2}.x=e^t,y=te^{-t}. For which values of t is the curve concave upward?

Differential equations
Find $$\frac{dy}{dx}$$ and $$\frac{d^2y}{dx^2}.x=e^t,y=te^{-t}$$. For which values of t is the curve concave upward?