Question

If ƒ(x) = 2x, then ƒ -1(x) =

1. -2x
2. ½x
3. x - 2

Answer 1

the answer is -2x. that should help

Answer 2

basically
1. replace f(x) with y
2. replace all y with x and all x with y
3. solve for y
4. replace y with f⁻¹(x)

so

f(x)=2x
replace
y=2x
switch
x=2y
divide both sides by 2
$\frac{x}{2}=y$
$y= \frac{x}{2}$
replace
$f^{-1}(x)= \frac{x}{2}$

the answer is the 2nd one