How do you integrate e power minus 2x?

∫e^(-2x) dx

Let u = 2x

du= 2 dx

dx=(1/2) du

∫e^(-2x) dx = (1/2) ∫e^-u du

= (1/2) (-e^-u)

= -e^-u /2 + C

= -e^-(2x) / 2 + C