Determine whether f is continuous at x=c in the function f(x)=x-1/x+1 at c=-1
The first condition or rule of continuity is that f(x) be defined at the point c.
f(-1) = (-1-1)/(-1+1) = -2/0
Division by zero is undefined, so f(x) is undefined at the point x=-1 and therefore not continuous at x=-1.