When x increases from a to a +2, y increases by a factor of 1/4

y=7* (0.5)^x

Step-by-step explanation:

We are given that when x increases from 'a' to 'a+2' then y must increase by a factor of 1/4=0.25.

i.e. when x=a and x'=a+2.

then y/y=0.25 where y' is the function after putting x' to the old function.

the least common denominator is 40