Question #29f86

2 Answers
Feb 5, 2018

#f^-1(-12) = -8#

Explanation:

The inverse of a function, #f^-1(y)#, reverses what the function, #f(x)#, does.

If #y = f(x)#, then #f^-1(y)=x#

Making this fit the context of your question

We are given that #f(-8) = -12#

The standard notation is #y = f(x)#, therefore, #y =-12# in this case. Then, using #f^-1(y) = x# gives us #f^-1(-12) = -8#

Feb 5, 2018

You would figure out #f(x)#, then find #f(-12)# and raise it to the #-1# power, a.k.a. find the reciprocal.

Explanation:

If #f(-8)=-12#, then what is #f(x)#? Well, #-8-4 = -12#, so #f(x)=x-4#. Then if #x=-12#, #f(x)=x-4 = f(-12)= -12-4 = -16#, so #f(-12)= -16#. Are we done? Nope. We are asked to find #f^-1(-12)#, not just #f(-12)#. That means we raise #f(-12)# to the power of #-1#.When you raise something to the #-1# power, you find the reciprocal. This is easy: just turn it into a fraction and flip it. #-16= -16/1#. Flip the fraction and you get #-1/16#. So if #f(-8)=-12#, then

#f^-1(-12)=-16#. We have our answer.