If is the first number in the progression, and is the common ratio between consecutive terms, then the first four terms in the progression are
We want to have
In the second equation, we have
and in the first, we have
Substituting this into the second equation, we find
So now we have
Then the four numbers are
The second one is correct so its 2
The answer is 3
5x = 16-1
5x = 15
x = 3
I hope this helps you
y+4/3=x^5
x= (y+4/3)^1/5
f^-1(x)=(x+4/3)^1/5