Question

how to find the squre root of the negative number

Answer 1

The square root of a negative number is an imaginary number. 

For example: $\sqrt{-2}$ can be written as ( $\sqrt{-1}$)( $\sqrt{2}$)

Here  $\sqrt{-1}$ is denoted by "i"

Answer 2

square roots of negative numbrs are not defined.... but using complex numbr we can define it  by i(iota) such that i square=-1
suppose if we have to find root-2= root  (2 i^2)=iroot 2