2x2 - 4x + 2 = 0Then x is algebraic.
- It is a non-zero polynomial
- x is a root (ie x gives the result of zero for the function 2x2 - 4x + 2)
- the coefficients (the numbers 2, 4 and 2) are rational numbers
The polynomial could, of course, be simpler or more complicated than this example, just so long as the coefficents are rational.
Not Algebraic? Then Transcendental!
If a number is not algebraic, it is called transcendental.
Example: is √2 (the square root of 2) algebraic or transcendental?
√2 is the solution to x2 - 2 = 0, so is therefore algebraic
All algebraic numbers are computable and therefore definable.
The set of algebraic numbers is countable.
The imaginary number i is algebraic (it is the solution to x2 + 1 = 0).
All rational numbers are algebraic, but an irrational number may or may not be algebraic.