Question 69123
<pre><font size = 4><b>Completely factor 

            {{{X^4-R^4}}}

That's the difference of two perfect squares.  
The fourth power is "the square of the square". 
So write the expression this way
 
            {{{(X^2)^2-(R^2)^2}}}

Then that factors as

           {{{(X^2 - R^2)(X^2 + R^2)}}}

But that's not finished yet, because what's in the first 
parentheses will factor some more.  It is the difference
of two perfect squares too.

      {{{(X-R)(X+R)(X^2+R^2)}}}

That's the final answer!

Warning: Do not try to factor further!

The DIFFERENCE of two squares {{{X^2-R^2}}} factors but
the SUM of two squares, such as {{{X^2+R^2}}} does not 
factor.

Edwin</pre>