The fastest way to find the missing endpoint is to determine from the known endpoint to the midpoint and then performing the same transformation on the midpoint.
I'm going to try to let you answer this yourself so you can learn for yourself ok. :3
ANSWER

EXPLANATION
The corresponding ordered pairs from the graph are:
(2,1) (3,2) (4,4) (5,8)
The y-values are:
1,2,4,8
The first term term is the term before 1,this has to be.

The common ratio is

The nth term is given by

Let's substitute the values to get,

This simplifies to,

3/5 3/4 7/8
As the higher the denominator and the higher the numerator or 'parts filled', the greater the fraction.
Answer : Slope = -4x/1
Explanation : The line is decreasing, which makes the slope a negative. And if you go down four spaces and to the right one space you have your slope.