Функцияның нөлдік мәнінің табылған жері

Point where function's value is zero

In mathematics, a zero (also sometimes called a root) of a real , complex , or generally vector valued function , is a member of the domain of such that vanishes at ; that is, the function attains the value of 0 at , or equivalently, is a solution to the equation A "zero" of a function is thus an input value that produces an output of 0. A root of a polynomial is a zero of the corresponding polynomial function. For example, the polynomial of degree two, defined by has the two roots (or zeros) that are 2 and 3. If the function maps real numbers to real numbers, then its zeros are the coordinates of the points where its graph meets the x axis. An alternative name for such a point in this context is an intercept.

Every real polynomial of odd degree has an odd number of real roots (counting multiplicities); likewise, a real polynomial of even degree must have an even number of real roots. Consequently, real odd polynomials must have at least one real root (because the smallest odd whole number is 1), whereas even polynomials may have none. This principle can be proven by reference to the intermediate value theorem: since polynomial functions are continuous, the function value must cross zero, in the process of changing from negative to positive or vice versa (which always happens for odd functions).

The fundamental theorem of algebra states that every polynomial of degree has complex roots, counted with their multiplicities. The non real roots of polynomials with real coefficients come in conjugate pairs. Vieta's formulas relate the coefficients of a polynomial to sums and products of its roots.

Computing roots of functions, for example polynomial functions, frequently requires the use of specialised or approximation techniques (e. g., Newton's method). However, some polynomial functions, including all those of degree no greater than 4, can have all their roots expressed algebraically in terms of their coefficients (for more, see algebraic solution).

In algebraic geometry, the first definition of an algebraic variety is through zero sets. Specifically, an affine algebraic set is the intersection of the zero sets of several polynomials, in a polynomial ring over a field. In this context, a zero set is sometimes called a zero locus. In analysis and geometry, any closed subset of is the zero set of a smooth function defined on all of This extends to any smooth manifold as a corollary of paracompactness. In differential geometry, zero sets are frequently used to define manifolds. An important special case is the case that is a smooth function from to If zero is a regular value of , then the zero set of is a smooth manifold of dimension by the regular value theorem. For example, the unit sphere in is the zero set of the real valued function .