I answered a question but I don't know if my answer is correct so I would appreciate if someone can confirm it. Thank you.
By the way I did some mistake when I wrote it. its an+1-an
Let . According to the question, . As romsek showed, the convergence of has nothing to do with the convergence of . But, we can use to look at properties of .
Check out . By limit laws, the limit of the difference is the difference of the limits, so long as both limits exist. Since both do, we know that . You can do the same for . So, if you define sequences , perhaps you can show that both of these sequences are Cauchy (using the previous results), and hence they both converge. Since convergent sequences are bounded, the original sequence must be bounded, as well.
Hmmmm, maybe we can take the sequence an=n , so we can say that an+1-an converges to 1? but an isn't bounded? Is this possible? i mean i know infinite minus infinite in limits is a problem but the distance between them should be 1 and it shouldn't be a problem right?(I got confused , this is completely wrong