Which function is strictly decreasing?
f(x)=exf(x) = e^xf(x)=ex
f(x)=ln(x)f(x) = \ln(x)f(x)=ln(x)
f(x)=e−xf(x) = e^{-x}f(x)=e−x
f(x)=x2f(x) = x^2f(x)=x2