4. For the curve :1: + y3 y = 1, complete the following steps. (a) Find equations of all lines tangent to the curve at :r = 1. (b) Graph the tangent lines on the given graph. (c) Determine the points where the curve has a vertical tangent line. (d) Does the curve have any horizontal tangent lines? Explain. 5. Determine whether the graph of y = :r has any horizontal tangent lines