I found this question interesting:
Which one of the following functions are equal to $f(x)=\lfloor \sqrt{x}-\lfloor \sqrt{x}\rfloor\rfloor$? ($\lfloor \cdot \rfloor$ is the floor function)
- $g(x)=\sqrt{x-|x|}$
- $g(x)=\sqrt{-x+|x|}$
- $g(x)=\sqrt{x+|x|}$
- $g(x)=\sqrt{-x-|x|}$
What I have done is to examine the domains of above functions regarding the fact that $0\leq x-\lfloor x\rfloor<1$. Just to share your ideas about this Maths multiple choices. Thanks.