Find the common ratio of the geometric sequence: −320,80,−20,5,…

With geometric sequences, if you divide a term by the term before it you'll get the common ratio. That's how they are all constructed, and in this problem:

So -1/4 is our common ratio.

yes because there is exactly one y value for every x value

for function there can't be more than one value for every x value

the expression (1.26)2t reveals the approximate rate of increases in the number of plants semiannually.

hope this : )