## Thomas' Calculus 13th Edition

An Elliptical paraboloid opening downward along $z$-axis as represented by $\bf{Graph(f)}$
Given: $z=-4x^2-y^2$ ...(1) or, $4x^2+y^2=-z^2$ Re-write as: $\dfrac{x^2}{(1/2)^2}+\dfrac{y^2}{1}=\dfrac{z}{-1}$ ...(2) Equation (2) shows a graph for an Elliptical paraboloid opening downward along $z$-axis as represented by $\bf{Graph(f)}$