Question

What is the common ratio for the geometric sequence? −15,−9,−275,−8125,..?

Answer 1

A geometric sequence is defined by the property that the ratio of two consecutive terms is always constants like this:$\frac{u_{n+1}}{u_n}=r$
Taking any two consecutive terms from the sequence e get:
$\frac{-9}{-15} \neq \frac{-275}{-9} \text{ since } \frac{3}{5} \neq \frac{-275}{-9}$

The sequence is not a geometric sequence 

Answer 2

The common ration to this problem is 3/5