Answer :

(x² - 1)^-2/3
∛(x² - 1)-²
∛(1/(x² - 1)(x² - 1))
∛(1/(x^4 - x² - x² + 1))
∛(1/(x^4 - 2x² + 1))
1/x^4/3 - 1.25992105x^2/3 + 1