If a curve is given by an equation of the form f (x, y) = 0, then the tangent li...

If a curve is given by an equation of the form f (x, y) = 0, then the tangent line to the curve at a given point (x0, y0) on it may be found in two ways: (a) by using the technique of implicit differentiation from single-variable calculus and (b) by using a formula analogous to formula (6). In Exercises 28–30, use both of these methods to find the lines tangent to the given curves at the indicated points.