Q.

The function defined by g(x)=x−[x] is discontinuous at:

1 all rational points  
2 all irrational points  
3 all integral points  
4 None of the above  

Ans.

(3)

Ans.     all integral points

Explanation:

The function f(x)=[x] is discontinuous at every integral point. Hence, the function g(x)=x−[x] is also discontinuous at every integral point.