Using an Equation Consider the equation $9 x^{2}+4 y^{2}-36 x-24 y-36=0$
(a) Classify the graph of the equation as a circle, a parabola, an ellipse, or a hyperbola.
(b) Change the 4$y^{2}$ -term in the equation to $-4 y^{2}$ Classify the graph of the new equation.
(c) Change the $9 x^{2}-$ term in the original equation to 4$x^{2}$ . Classify the graph of the new equation.
(d) Describe one way you could change the original equation so that its graph is a parabola.