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This implies that at a local minimum the Hessian is positive-semidefinite, and at a local maximum the Hessian is negative-semidefinite. For positive-semidefinite and negative-semidefinite Hessians the test is inconclusive (a critical point where the Hessian is semidefinite but not definite may be a local extremum or a saddle point).
The gradient of F is then normal to the hypersurface. Similarly, an affine algebraic hypersurface may be defined by an equation F(x 1, ..., x n) = 0, where F is a polynomial. The gradient of F is zero at a singular point of the hypersurface (this is the definition of a singular point). At a non-singular point, it is a nonzero normal vector.
In economics, a normal good is a type of a good which experiences an increase in demand due to an increase in income, unlike inferior goods, for which the opposite is observed. When there is an increase in a person's income, for example due to a wage rise, a good for which the demand rises due to the wage increase, is referred as a normal good.
The Lorenz curve is invariant under positive scaling. If X is a random variable, for any positive number c the random variable c X has the same Lorenz curve as X. The Lorenz curve is flipped twice, once about F = 0.5 and once about L = 0.5, by negation. If X is a random variable with Lorenz curve L X (F), then −X has the Lorenz curve:
Letting be the quantity of output produced (to be chosen), () be sales revenue with a positive first derivative and with a zero value at zero output, () be production costs with a positive first derivative and with a non-negative value at zero output, and be the positive minimal acceptable level of profit, then the problem is a meaningful one ...
This is the case in economics with respect to the ordinal properties of a utility function being preserved across a monotonic transform (see also monotone preferences). [5] In this context, the term "monotonic transformation" refers to a positive monotonic transformation and is intended to distinguish it from a "negative monotonic ...
Since the price elasticity of demand is negative for the vast majority of goods and services (unlike most other elasticities, which take both positive and negative values depending on the good), economists often leave off the word "negative" or the minus sign and refer to the price elasticity of demand as a positive value (i.e., in absolute ...
In the philosophy of economics, economics is often divided into positive (or descriptive) and normative (or prescriptive) economics.Positive economics focuses on the description, quantification and explanation of economic phenomena, [1] while normative economics discusses prescriptions for what actions individuals or societies should or should not take.