By considering the set of points P(x, y) that are equidistant from the two lines represented by the equation $\displaystyle ax^2+2hxy+by^2=0$ show that the equation of the pair of angle bisectors of these lines is

$\displaystyle hx^2+(b-a)xy-hy^2=0$

I know that the pair of lines that are bisectors are perpendicular to each other and all the lines intersect at the origin. I don't know what else, or how to begin.

Thanks!