Question 1175216
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This apparently requires a factorization technique that I am not familiar with.<br>
I went to wolframalpha.com and entered "factor ab^3 - a^3b + bc^3 - b^3c + ca^3 - c^3a" and it did it:<br>
{{{ab^3 - a^3b + bc^3 - b^3c + ca^3 - c^3a = (a-b)(b-c)(c-a)(a+b+c)}}}<br>
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If you're not familiar with wolframalpha.com, you should be.  It's amazing -- it will do almost anything....<br>