#### Answer

$r= \frac{3}{1 - cos(θ)}$

#### Work Step by Step

$r= \frac{ed}{1 + e cos(θ)}$
e = 1 since it is an parabola, directrix is at x=-3. Origin is at (0,0) so d= 3, but it will be - cos(θ) since the directrix is negative
$r= \frac{(1) (3)}{1 - (1) cos(θ)}$
$r= \frac{3}{1 - cos(θ)}$