Question

What is the domain of the function f(x) = -2x + 6 when the range is {-2, 2, 4}?

Answer 1

To do this, we have to solve the equation 3 times for 3 different values for f(x).
Those three numbers are -2, 2, and 4, the numbers in the range. 
First solve for -2. 
-2 = -2x + 6 
Subtract 6 from each side:
-8 = -2x 
Divide by -2 on each side:
4 = x       That's one value done. 

Next, solve with 2. 
2 = -2x + 6 
Subtract 6 from both sides.
-4 = -2x 
Divide each side by -2. 
2 = x         Second value solved for. 

Last value: 4. 
4 = -2x + 6 
Subtract 6 from each side. 
-2 = -2x 
Divide each side by -2. 
1 = x.       Now just put the domain together. 

Domain is this: 
{4, 2, 1}.
Hope this helps!