Question 82239
Evaluate:
{{{sqrt(-100)}}}

The square root of a negative number is not a real number.
You can see why when you ask "What number, when squared, gives a negtive result?"
The answer is, of course, there isn't one...well, not a real one!
Why is that?
When you square a number, you multiply that number by itself, so the numbers will have the same sign (both + or both -).
The rules of multiplication indicate that when you multiply two numbers having the same sign, the answer will alwys be positive.
Therefore, you cannot find a real number by taking the square root of a negative number.
What do you get when you try, for example, to take the square root of -100?
{{{sqrt(-100) = sqrt(10*10)}}} =  {{{10sqrt(-1)}}}
Now {{{sqrt(-1)}}} is called an "imaginary" number and is given the special symbol of "i".
So...{{{sqrt(-100) = 10i}}}