Question

If the range of the function f(x) = 4 − 4x is {-20, -16, -8, 0, 4}, what is its domain?

A) {0, 1, 2, 4, 6}
B) {2, 3, 5, 6, 7}
C) {1, 3, 5, 7, 9}
D) {0, 1, 3, 5, 6}

Answer 1

@amistre64

Answer 2

Im thinking you plug in each range or 'y' value and get its corresponding x value, then put them all together for the domain. so for the first one

-20=4-4x
x=?

Answer 3

How do I figure out 'x'? Sorry, really bad at this, which is why I'm asking for assistance xD.

Answer 4

Alrighty, just solve for x like you would any equation

subtract 4 from both sides

-20-4=-4x
-24=4x

divide both sides by -4
-24/-4=x
6=x

so thats one value for the domain, next one you need to solve

-16=4-4x

Answer 5

-20=4-4x
-16=4-4x
-8=4-4x
0=4-4x
4=4-4x
solve each and find the value of x.

Answer 6

Okay, so now I would go like so..

-16=4-4x

Now subtract 4 from both sides, which would bring in result of

-16-4=4x
-20=4x

Then divide both sides by 4 and that would be

-20/4=4x/4

-5=x

Correct?

Answer 7

Close, forgot the negative sign on -4x

-20/-4=-4x/-4
5=x

Answer 8

now for

-8=4-4x

Answer 9

Ok.

-8=4-4x

-8-4=-4x

-12=-4x

-12/-4=-4x/-4

Which in final results is

3=x. Right?

Answer 10

You've got it.
next one
0=4-4x

and then
4=4-4x

Answer 11

0=4-4x

0-4=-4x

-4=-4x

1=x, right? for the first one..

Then

4=4-4x

4-4=-4x

0=-4x

0=x, correct?

Answer 12

Yep, now put all of our answers together from smallest to largest..

{0,1,3,5,6}

Answer 13

Thank you so much, you were an extremely big help! :) This was confusing the heck outta me. Now thanks to you, I got it! THANKS SO MUCH! (:

Answer 14

You're welcome

Answer 15

correction
-16=4-4x
-16-4=-4x
-20=-4x
\[\frac{ -20 }{-4 }=x or x=5\]
similarly
for others