Finding equilibria of nonlinear coupled differential equations requires solving nonlinear simultaneous equations that can have any number of solutions. For each of the following pairs, solve each equation for y in terms of x, set the two equations for x equal, and solve for x. Check that both equations give the same value for y. Sketch a graph with y on the vertical axis.
-y2 + x2 = 0
-2 + 2y - 4x = 0
Solving the first equation for y in terms of x does not give a function. Graph the relation and find the solutions.