Question

the function f(x) = x*x - 1 / x - 1 is discontinuous at x = 1 because

Answer 1

is it defined at x=1?

Answer 2

what is domain of function?

Answer 3

denominator must be different from zero
\[x-1 \neq 0 \rightarrow x \neq 1\]
in this point function simply doesn't exist ( you cannot divide by zero)
that's why it's discountinuous