Hi, I am having trouble with contours, is there a procedure to do these?

the question I am working on is when z=c

z=((x^2)+(y^2))/2x

what i tried to do:

c2x=(x^2)+(y^2)

c2x-x^2=y^2

x(2c-x)=y^2

2c-x=(y^2)/x

2c=((y^2)/x)+x

and that is where I got stuck. I cant visualize what is going on here

thanks for any replys :)