if the number bunnies doubles every day and , on day 1 ,you start with 25 bunnies , what exponential equation best models this scenario

If the number of bunnies doubles every day, then you always have to multiply the preceding day's number by 2.

If you use:  y  =  25·2^x-1

Then:  day 1:  x = 1  --->  y  = 25·2^1-1  =  25·2⁰  =  25·1  =  25

           day 2:   x = 2  --->  y  = 25·2^2-1  =  25·2¹  =  25·2  =  50

           day 3:   x = 3  --->  y  = 25·2^3-1  =  25·2²  =  25·4  =  100

           day 4:   x = 4  --->  y  = 25·2^4-1  =  25·2³  =  25·8  =  200

etc.

f(X)=25(2)x