How do you simplify (x^2 - 1) /(x^2 - 3x - 10)*(x^2 + 5x + 6)/ (x^2 - 3x – 4)*(x^2 - x - 20)/(x^2 + 2x – 3)?

$\frac{\left(x - 1\right) \left(x + 1\right)}{\left(x + 2\right) \left(x - 5\right)} . \frac{\left(x + 2\right) \left(x + 3\right)}{\left(x + 1\right) \left(x - 4\right)} . \frac{\left(x + 4\right) \left(x - 5\right)}{\left(x - 1\right) \left(x + 3\right)}$ =
= $\frac{x + 4}{x - 4}$