Using an LLM with CAS math validation tools to validate it's work and then to generate a markdown document with CAS blocks:

  :::cas mode=chain engine=sympy assumptions="x \neq 1"
  $$ \frac{x^2 - 1}{x - 1} $$
  $$ = \frac{(x-1)(x+1)}{x-1} $$
  $$ = x + 1 $$
  :::

Which you can run to check it.