Principal Value of a Square Root
A square root of a number b is the solution of the equation x2 = b. It is a number that when multiplied by itself gives you b. Every positive number b has two square roots, denoted 
and – . The principal square root of b is the positive square root, denoted .
Example 1:
The square roots of 25 are 
and 
since 52 = 25 and (–5)2 = 25.
The principal square root of 25 is 
Example 2:
Find the real roots of the equation x2 = 100.
Therefore the roots are 10 and –10.
Example 3:
Simplify 
indicates the principal (or positive) square root so 
