The question: Find the equation of the locus of the point which is equidistant from the y-axis and the point (3,-1).

So I let the variable point be P(x,y)

for the y-axis I use A(0,y)

and I call the given point B(3,-1)

I then form the equation PA^2=PB^2 and solve.

I can't seem to find the correct answer. If anyone could point out what I'm doing wrong I'd really appreciate it