If the n + 1 numbers a, b, c, d, .... be all different, and each of them a prime number, prove that the number of different factors of the expression .... is
My Self Assessment
If of p + q + r things p be alike, and q be alike, and the rest different, show that the total number of combination is .
Show that the number of permutations which can be formed from 2n letters which are either a’s or b’s is greatest when the number of a’s is equal to the number of b’s.
.... is 
