forgive me for my horrible english (I'm italian and I'have registred for this forum to test my language skills and to better understand the maths).

This is my question: how can i prove with the Newton's binomial that . Obviously is easy adding 1 with 1, but the book where i've found this exercise (it's "what's the mathematics?", Courant and Robbins, it's very famous) explicitly ask to use the binomial's theorem.

Thanks for the attention and for the patience.

P.s: How can I write the binomial's Coefficients on the forum?