i stands for imaginary number, $${i} = {\sqrt{-{\mathtt{1}}}}$$.

this is because no number squared can equal a negative number

$${\left(-{\mathtt{1}}\right)}^{{\mathtt{2}}} = \left(-{\mathtt{1}}\right){\mathtt{\,\times\,}}\left(-{\mathtt{1}}\right)$$

a negative times a negative is a positive so the answer is just 1

positive times positive is also positive so you get 1.

if a math problem asked you for the square root of a negative number you either learned about it already or somewhere else you made a mistake.

good luck yo