Answer
The recursive formula is $a_{1}$=1 and $a_{n}$=$a_{n-1}$ $\times$ 5.
Work Step by Step
Use the recursive formula $a_{1}$=1, $a_{n}$=$a_{n-1}$$\times$r.
The starting value is 1 so it is the $a_{1}$
You have the sequence 1,5,25 so use the common ratio formula(r=$\frac{{a_{2}}}{{a_{1}}}$) r=$\frac{5}{1}$=5 and r=$\frac{25}{5}$=5.So the common ratio is 5.Substitute the value of a1 and R into the recursive formula:
The recursive formula is $a_{1}$=1 and $a_{n}$=$a_{n-1}$ $\times$ 5.
