# ISI B.Math Entrance(6)

Algebra Level 4

Find the number of discontinuities in the function $$f(x)=(x+1)\text{sgn }(x^2-1)$$, where $$f: \mathbb R \to \mathbb R$$, where $$\mathbb R$$ is the set of all real numbers.



Notation: $$\text{sgn }(\cdot)$$ denotes the sign function.

×