Question

If f(x) = 5x, what is f–1(x)?

A. f–1(x) = –5x
B. f-1(x)=-1/5x
C. f-1(x)=1/5x
D. f–1(x) = 5x

Answer 1

The answer is C.

Explanation:

Step 1: Replace f(x) with y.

f(x)=5x >>>>> y=5x

Step 2: Switch x and y.

y=5x >>>>> x=5y

Step 3: Solve for y

x=5y >>>> y= x/5

Then you have to do the inverse of dividing by 5. Which is multipilying by 1/5. This leaves you with,

y= 1/5x

Step 4: Write in standard inverse notation (Replace y with f^-1(x))

f^-1(x)=1/5x

Note: These steps work with ANY problem where you have to find the inverse function. I hope this helps :)

Answer 2

To get the inverse of a function interchange
the x's with the y'x and solve for y, as follows:
y=5x-7

Interchange to get:
x=5y-7
Solve for y to get:
y=(1/5)x+(7/5)

so I think it might be c