Original question: Find an equation of the level curve of f(x,y) = yx^2 – y^2 through the point (2,1) and find an equation of the tangent line to the level curve at this point. I think I have found the equation of the tangent line to the level curve: 10 = 4x + 2y (is this correct??), but I have no idea how to find the equation of the level curve. Please help! Thank you!!