<em>Note: Your question seems a little bit ambiguous. So, I am assuming the given function f(x)=9x+7.</em>
<em>Thus, I am solving based on it. It would still clear your concept. </em>
Answer:
The inverse of f(x)=9x+7
Step-by-step explanation:
Given the function

A function g is the inverse of function f if for y=f(x), x=g(y)
Replace x with y

solve for y


Therefore,
The inverse of f(x)=9x+7 is:
i.e.

There is NO MODE for the data set because none of the numbers are repeated at least once.
I guess you are asking to find the sum of the first 8 terms. If so, then:
Sum = a₁(1-rⁿ)/(1-r), where a₁ is the 1st term, r=common ratio and n=number of terms:
the 1st term a₁ =3
common ratio r = - 2 (since -6/3 = - 2, and 12/-6 = - 2, etc.)
Sum = 3[(1- (-2)⁸]/(1-2) = 3(1- 256)/(1/2)
Sum = -1530