# Use sigma notation for expression

1. Apr 7, 2009

### synergix

1. The problem statement, all variables and given/nknown data
Find a formula for the expression. Use sigma notation.
(x + 1/y)n

3. The attempt at a solution

Not sure how to do this we have only dealt with sigma notation involving only n as a variable

2. Apr 8, 2009

### dx

Use the binomial theorem to expand the expression.

Example:

$$\sum_{n=1}^{5} x^n = x + x^2 + x^3 + x^4 + x^5$$​

Notice that although x is a variable, it does not vary from term to term. The only thing that varies from term to term is the exponent. Your problem is similar.