Hi Guys,

Need a little help with this one, Not sure how to proceed.

Two positive integers,

are connected by the relation

. By using a binomial expansion show that for all positive integral values of n the expression

is exactly divisible by

. By choosing suitable values of a and n, show that

is divisible by 9, and hence that

is divisible by 9.

I tried putting the substitution for

into the equation, and did a binomial expansion of

, but not sure where that is supposed to lead. It seems like another longer equation.

Thanks for your help.