Google Answers: Answering square roots

What is the square root of 25? The answer should obviously be 5,
since 5*5=25. But could -5 work as well such as, -5 * -5 = 25. If
the latter is true, what would be the answer to negative of a square
root of 25 (-(v25))? Would it still be positive and negative 5?

Hi hookem03,
Like other positive real numbers, 25 has two square roots, 5 and -5. 
As you guessed, the negative of the square root of 25 is the same two
numbers, since the 5 becomes -5 when negated, and similarly, the -5
becomes 5.
The positive square root is called the "principal square root," and in
some contexts, that may be what is meant by a reference to the square
root of a number. But both the positive and negative square roots
really are square roots.
Additional Links
Wikipedia on square roots
http://en.wikipedia.org/wiki/Square_root
Square root article on Wolfram MathWorld
http://mathworld.wolfram.com/SquareRoot.html
--efn