If [math]x + y = 2[/math] and [math] x^2 + y^2 = 2[/math], what is the value of [math]xy[/math]?
How do I solve [math](x^2 -xy) \frac{dy}{dx} +y^2 =0[/math] with initial values [math]x=e[/math], [math]y=e[/math]?