3. The line \(L\) has equation \(y = 5 - 2 x\).
- Show that the point \(P ( 3 , - 1 )\) lies on \(L\).
- Find an equation of the line perpendicular to \(L\), which passes through \(P\). Give your answer in the form \(a x + b y + c = 0\), where \(a , b\) and \(c\) are integers.