I need helping forming the equation given in the question, any help?

The sum of the first three terms of a geometric progression is 14. If the first term is 2, and the common ratio isr,show thatr^{2 }+ r - 6 = 0

I tried substitutinga = 2andn = 3into the geometric formula for the sum of a series, such that2(r, but I can't get it to equal anything near the equation given in the question, so I think I'm doing something wrong...^{3 }- 1) / (r - 1) = 14