A real-valued function defined on a convex subset is said to be quasi-convex if for all real , the set is convex. This is equivalent to saying that is quasi-convex if and only if its negative is quasi-concave.
Quasi-Convex Function
See also
Convex, Convex Function, Pseudoconcave Function, Pseudoconvex Function, Quasi-Concave FunctionThis entry contributed by Christopher Stover
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References
Borwein, J. and Lewis, A. Convex Analysis and Nonlinear Optimization: Theory and Examples. New York: Springer Science+Business Media, 2006.Cite this as:
Stover, Christopher. "Quasi-Convex Function." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/Quasi-ConvexFunction.html