y=x^2
therefore,
x^2=3,x^2=2
x=sqrt(3),x=sqrt(2)

This gives us all the four values of x
How?
For example sqrt(16)=-4,+4
This is because when a number is squared,
-*-=+ and +*+=+
In other words,a negative number squared is positive,a positive number squared is also positive,so -4 or +4 squared will give the same result.

So our correct answer is:
x=+sqrt(3),-sqrt(3),+sqrt(2),-sqrt(2)

Hope this helps,
Prabhat