Question 30168
Do you know about Imaginary Numbers?
We know that the square of a number is always Positive.
What if there exists such a number whose square is always Negative? Such a number is called Imaginary Number and is denoted by the letter "i"
So {{{i*i = i^2 = -1}}}

So {{{-121 = 121i^2}}}
{{{sqrt(121i^2)}}}

121 = 11*11
So your final answer = 11i