Consider the graph of x^2 + 2*x + y^4 + 4*y = 5
(A) what is dy/dx
(B) Write an equation for the line tangent to the curve at the point (-2,1)
(C) Find the coordinates of the two points on the curve where the line tangent to the curve is vertical
(D) Is it possible for this curve to have a horizontal tangent at the points where it intersects the x-axis? Explain your reasoning.
