Question

How do you remove discontinuity of `f(x) = (x^4 - 1)/(x-1)`?

Answer 1

You can write your numerator as `(x^2-1)(x^2+1)` where `(x^2-1)=(x-1)(x+1)` giving:
`f(x)=((x-1)(x+1)(x^2+1))/(x-1)=(x+1)(x^2+1)`