Hello erisse_satg17Welcome to Math Help Forum.

This is what you need to know. In a GP:

- the first term is denoted by
- the common ratio is denoted by
- the first three terms are
- the sum of the first terms is
- the sum to infinity is , provided

So you'll need to plug in the values you've been given:

and

and solve for and . (Don't forget to answer the question when you done this.)

Can you complete it now?

Grandad