If you are doing Exercise 34 in the Project Gutenberg edition, the answer is that these two problems are typos. You can read the original at Google Books e.g. here: the problems should be
$1$. Factor $x^3+y^3$ (was incorrectly printed as $x^5+y^5$ in the Gutenberg version)
$5$. Factor $8a^3b^3c^6+m^6$ (was incorrectly printed as $8a^5b^3c^6 + m^6$ in the Gutenberg version)
There are solutions to the exercises in the back of the book.