For the function f(x)= (8-2x)^2, find f^-1. determine whether f^-1 is a function.

No its not a function :) 

to find the inverse function first expand those brackets 

you'll get 
f(x)= x^2 - 2x^2 - 2x^2 = 4x^2 
f(x)= x^2 - 4x^2 + 4x^2 
f(x)= x^2 or y=x^2 

to find the inverse, swap x and y around. then make y the subject again 

y=x^2 
x=y^2 
Root of x=y 

now put -1 into x 

it wont work because roots cannot have negative numbers 
answer is no

Dis the correct answer

So don't take my word i'm not exactly a mathematical person but i would assume a. because while selling the soap every month you increase in sells so you would by 11 percent. the you would get the factor 0.89 which if i had to guess would be the monthly profit over 11 probably wrong tho