Answer
$r=-5 \sin \theta$
Work Step by Step
Consider $x^2+y^2+5y=0$
or, $x^2+(y+\dfrac{5}{2})^2=(\dfrac{25}{4})$
Here, we get the equation of a circle with center $(0,-\dfrac{5}{2})$ and radius $\dfrac{5}{2}$
Thus,
$r^2+5r \sin \theta=0 \implies r=-5 \sin \theta$
