How did we get it here?

Question

Mathematics

How did we take away 2 options here? for example, 1 subtraction term (1 / (n+1)!) is the result of subtracting which terms from yn+m and yn?

Answer 1

The first formula should contain n!, not k!.
The difference is the last m terms of y _m+n = 2 + 1/2! + ... + 1/n! + 1/(n+1)! + ... + 1/(n+m)!