Skip to main content\(\newcommand{\R}{\mathbb{R}}
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A three dimensional plot with axes labeled
\(x\text{,}\) \(y\text{,}\) and
\(z\) and a grid on the xy-plane. A curved surface is shown in light blue. The surface curves up along the directions given by the x and y axes and down in directions where
\(x=\pm y\text{.}\) The upward curved path of the surface above the x and y axes is highlighted in red.