Thank you for the exact statement of the problem. In this case, it would have helped had you said what you were studying currently. I am going to guess that it is the binomial expansion and provide a BIG hint.
[MATH](a + b)^m = \sum_{j=0}^m \dbinom{m}{j} * a^j * b^{(m-j)}[/MATH].
Have you ever seen that?
There is a special case
[MATH](1 + b)^m = \sum_{j=0}^m \dbinom{m}{j} * 1^j * b^{(m-j)} = \sum_{j=0}^m \dbinom{m}{j} * b^{(m-j)} = \sum_{k=0}^m \dbinom{m}{k} * b^k.[/MATH]
Can you justify EACH of those steps?
Now do you see something in your problem that looks like that final expression?