1. ## Continuous random variables

Hi,

I have tried to algebraically manipulate this equation in order to obtain k, however my attempts have been unsuccessful.
\displaystyle \begin{align*} \int_{-\infty}^{\infty}{f\left( y \right) \,\mathrm{d}y} &= 1 \\ \int_{-\infty}^0{0\,\mathrm{d}y} + \int_0^{\infty}{ k\,\mathrm{e}^{-y}\,\mathrm{d}y } &= 1 \\ 0 + \int_0^{\infty}{ k\,\mathrm{e}^{-y}\,\mathrm{d}y } &= 1 \\ k\int_0^{\infty}{\mathrm{e}^{-y}\,\mathrm{d}y} &= 1 \end{align*}