Question 990496
<pre>
{{{(a^2+b^2) (-a^2+b^2)}}}

Reverse the terms in the second parentheses so the positive
term comes first and the negative term comes second.

{{{(a^2+b^2)(b^2-a^2)}}}

Now the second parentheses can be factored as the difference
of two squares:

{{{(a^2+b^2)(b-a)(b+a)}}}

Edwin</pre>