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This application also invokes the integer root theorem, a stronger version of the rational root theorem for the case when () is a monic polynomial with integer coefficients; for such a polynomial, all roots are necessarily integers (which is not, as 2 is not a perfect square) or irrational. The rational root theorem (or integer root theorem ...
This polynomial has no rational roots, since the rational root theorem shows that the only possibilities are ±1, but x 0 is greater than 1. So x 0 is an irrational algebraic number. There are countably many algebraic numbers, since there are countably many integer polynomials.
A real number that is not rational is called irrational. [5] Irrational numbers include the square root of 2 ( ), π, e, and the golden ratio (φ). Since the set of rational numbers is countable, and the set of real numbers is uncountable, almost all real numbers are irrational. [1]
Moreover, if one sets x = 1 + t, one gets without computation that () = (+) is a polynomial in t with the same first coefficient 3 and constant term 1. [2] The rational root theorem implies thus that a rational root of Q must belong to {,}, and thus that the rational roots of P satisfy = + {,,,}.
It includes all quadratic irrational roots, all rational numbers, and all numbers that can be formed from these using the basic arithmetic operations and the extraction of square roots. (By designating cardinal directions for +1, −1, + i , and − i , complex numbers such as 3 + i 2 {\displaystyle 3+i{\sqrt {2}}} are considered constructible.)
Hence, the set of real numbers consists of non-overlapping sets of rational, algebraic irrational, and transcendental real numbers. [3] For example, the square root of 2 is an irrational number, but it is not a transcendental number as it is a root of the polynomial equation x 2 − 2 = 0.
The square root of the Gelfond–Schneider constant is the transcendental number = 1.632 526 919 438 152 844 77.... This same constant can be used to prove that "an irrational elevated to an irrational power may be rational", even without first proving its transcendence.
The square root of 2 is irrational, and 3 is rational. is also irrational: if it were equal to , then, by the properties of logarithms, 9 n would be equal to 2 m, but the former is odd, and the latter is even. A more substantial example is the graph minor theorem.