First of all apologize for my english, I'm french and I'll do my best to be understandable. So my question is about factorials. how do you manage to say that (n+1)!=(n+1)n! ? I tried to develop this but my brain is just not able to understand how I'm suppose to do. Could someone please show me how to develop them? I'm actually doing a problem that requires me to "symplify" (is it the word?) (2n)! and (2(n+1))! and I'm stuck there. thanks for your help.