Example 5 -- Finding Absolute Extrema

Plot3D[x^2 + y^2 + x^2 * y + 4, {x, -1, 1}, {y, -1, 1}]

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Plot3D[x^2 + y^2 + x^2 * y + 4, {x, -1, 1}, {y, -1, 1}, ViewPoint {0, -2, 0}]

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ts = Table[t, {t, 2, -2, -.5}] ;

Do[Plot3D[x^2 + y^2 + x^2 * y + 4, {x, -1, 1}, {y, -1, 1}, TicksNone, ViewPoint {0, -2, ts[[t]]}], {t, 1, Length[ts]}]

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ContourPlot[x^2 + y^2 + x^2 * y + 4, {x, -1, 1}, {y, -1, 1}, ContourShadingNone, Contours20]

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Created by Mathematica  (December 11, 2003)