An algebraic number is any real or complex number that is a solution of an equation of the form 
An algebraic number is any real or complex number that is a solution of a polynomial equation of the form 
All rational numbers are algebraic because every fraction a / b is a solution of bx  a = 0. Some irrational numbers such as 2^{1/2} (the square root of 2) and 3^{1/3} (the cube root of 3) are also algebraic because they are the solutions of x^{2}  2 = 0 and x^{3}  3 = 0, respectively. But not all real numbers are algebraic. Examples of this are π and e (the natural logarithm base). 
All rational numbers are algebraic because every fraction a / b is a solution of bx  a = 0. Some irrational numbers such as 2^{1/2} (the square root of 2) and 3^{1/3} (the cube root of 3) are also algebraic because they are the solutions of x^{2}  2 = 0 and x^{3}  3 = 0, respectively. But not all real numbers are algebraic. Examples of this are π and e. If a complex number is not an algebraic number then it is called a transcendental number. 
It can be shown that if we allow the coefficients a_{i} to be any algebraic number then the solution of the equation will also be an algebraic number. If a complex number is not an algebraic number then it is called a transcendental number. 
The sum, difference, product and quotient of two algebraic numbers is again algebraic, and the algebraic numbers therefore form a field. It can be shown that if we allow the coefficients a_{i} to be any algebraic numbers then every solution of the equation will again be an algebraic number. This can be rephrased by saying that the field of algebraic numbers is algebraically closed. In fact, it is the smallest algebraically closed field containing the rationals, and is therefore called the [algebraic closure]? of the rationals. 
