收拾东西刚好看到娃Calc BC的考试题。大家可以作作看 ： ）

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.