I have

x^2 +xy

I want to sketch level curves for it but I'm stuck at simplifying it. I can factor out the x or complete the square but how do I find out what the curve is?

so another form is

(x+½y)^2 - 0.25y^2

so if I let c = 2 for example I'll get

(x+½y)^2 - 0.25y^2 = 2

what do I do now?