We can let $u = x^2 - 1$. Then, we have $du = 2x\,dx$. Now, we can rewrite the integral in terms of $u$:
$$\int x(x^2 - 1)^2\,dx = \frac{1}{2}\int u^2\,du$$
Now, we can integrate with respect to $u$:
$$\frac{1}{2}\int u^2\,du = \frac{1}{2}\cdot\frac{1}{3}u^3 +
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