#10 Help ​

10

The nth term is given  by :

64 (1/4)^n-1

so.....the 10th term is    64 (1/4)^{10 - 1}  =  64 (1/4)⁹  = 1 / 4096

11      35   ___    875

875 / 35   = r^2

25  = r^2       take both  roots

5  = r    or  - 5  = r

So ......the missing term is   35 * (5)  = 175 

Or......the missing term is  35 (-5)  =  -175