Question 884962
why square root of -2 is not a real number and what we have to see a number is real or not 
solution
square root of negative number not defined as we know square root of 4 is +2 and -2  when we take square root of negative it self . it can not defined 
for this purpose sqrt of (-2) can be written as squrt 2 x sqrt (-1)

sqrt (-1) is term as imaginary number i (iota) 
therefor  sqrt (-2) = squrt 2 x sqrt (-1) = sqrt 2 xi which is again Imaginary number 
so real number ( rational or irrational ) or which can be represent on number line  is known as real number or which is sqrt with positive number is real 
number which can not be represent on number line  is Imaginary number  or sqrt of negative number is Imaginary
combination of real and Imaginary is called complex number represent as Z
Z=X +iy where X is real and Y is imaginary