Upgrading from:

Graphics`InequalityGraphics`

New functions RegionPlot and RegionPlot3D have been added to the built-in Mathematica kernel.
RegionPlot includes the functionality of InequalityPlot.
RegionPlot3D includes the functionality of InequalityPlot3D.

RegionPlot displays the two-dimensional region defined by a set of inequalities:

Version 5.2 << Graphics`InequalityGraphics`; InequalityPlot[x^2 ≤ y^3 + y^2 - 5 y + 1, {x, -2, 2}, {y, -2, 2}]

RegionPlot3D displays the three-dimensional region defined by a set of inequalities:

Version 5.2 InequalityPlot3D[ x^2 + y^2 + z^2 ≤ 1 && 3 x^2 + 3 y^2 ≤ z^2, {x, -1, 1}, {y, -1, 1}, {z, -1, 1}]

ComplexInequalityPlot was available in previous versions of Mathematica and is now available on the web at library.wolfram.com/infocenter/MathSource/6817.