BITSAT 2018 Paper

If x≥0, then [x] is an integer part of x.
Hence x2≥[x]2 and f(x)=√x2−[x]2 is well-defined.
If x<0 say x=− a where a is a positive number,
then [x]=−([a]+1)
Hence, x2<[x]2 and the function f(x)=√x2−[x]2 is not defined.
Therefore the domain of the function is [0,∞).