Question 23908
<pre><b><font size = 4>        (a<sup>2</sup>-4a-1)<sup>2</sup> - 16

        (a<sup>2</sup>-4a-1)<sup>2</sup> - 4<sup>2</sup>

        <font color="red">(a<sup>2</sup>-4a-1)</font><sup>2</sup> - <font color = "blue">4</font><sup>2</sup>    that's the difference of two squares

  [<font color="red">(a<sup>2</sup>-4a-1)</font> - <font color = "blue">4</font>][<font color="red">(a<sup>2</sup>-4a-1)</font> + <font color = "blue">4</font>]

[a<sup>2</sup> - 4a - 1 - 4][a<sup>2</sup> - 4a - 1 + 4]

   [a<sup>2</sup> - 4a - 5][a<sup>2</sup> - 4a + 3]

 [(a - 5)(a + 1)][(a - 3)(a - 1)]

   (a - 5)(a + 1)(a - 3)(a - 1)

Edwin
AnlytcPhil@aol.com</pre>