(a) Write an equation in $x$ and $y$ for an arbitrary line $l$ that passes through the origin.
(b) Verify that if $P(a, b)$ lies on $l$ and $\alpha$ is a real number, then the point $Q(\alpha a, \alpha b)$ a)so lies on $l$
(c) What additional conclusion can you draw if $\alpha>0 ?$ if
$\alpha<0 ?$