Question

What is the range of the function f(x) = 12 − 3x for the domain {-4, -2, 0, 2, 4}?

Answer 1

To find the range, you need to plug in each domain into the equation and find the resulting value. That will be the range.

Answer 2

but adding on to @AbdullahM you could also just take the smallest and largest values of domains to plug in

Answer 3

since for range u just need to know the smallest and biggest value

Answer 4

For example, plug in -4

f (-4) = 12 - 3 (-4)

Answer 5

however if it's a quadratic function then you probably have to draw a graph

Answer 6

@wcrmelissa2001 not always. This question doesn't want a range of the range. It wants each range for each of the domains.

Answer 7

so just substitute x with the domains?

Answer 8

Correct

Answer 9

Not each of the domains. Everything inside the bracket is the domain itself. The whole thing is one domain so you can just take the smallest and largest value.

Answer 10

because what if the domain is (and there are such questions) where the domain is x is a real number. There is no way you can test all of that :(

Answer 11

Thank you guys!

Answer 12

@wcrmelissa2001 you are wrong.

Answer 13

would I do the same thing with this question? If the range of the function f(x) = 7x – 2.7 is {14.1, 30.9, 41.4, 58.9, 68}, what is its domain?

Answer 14

For this question you replace f (x) with the range, and solve for x.

Answer 15

@AbdullahM how so? (note that I don't mean this in a mean way, I genuinely want to know esp if I'm wrong)

Answer 16

because I see that if you were to plot a graph, in the end the range would be the largest and smallest values of the domain would it not?

Answer 17

You see, when you have a function, it can have a domain of all real numbers. But once they give you a domain of a set of numbers, the range is only restricted to that domain.

Answer 18

which is why you take the smallest and largest values of the domain to plug in for this example?

Answer 19

No. A function has infinity of points, so that is why we use a range of numbers to show what the domain and range are in between.

But when you give a domain, that means only these numbers can go into the function to find the range. When you are given a set of domain, the range is related to each one of the domajns.

Answer 20

So for example I'd write f(14.1)=7x-2.7 to solve?

Answer 21

yes precisely. so since the domain is restricted you can just take the smallest and largest values of this restricted domain to find the corresponding range of this restricted domain

Answer 22

@JamesS219 srry I would answer but I'm having doubts about my own understanding

Answer 23

Wcr, if the domain is 1, 100, and 1000, then if you do it your way, you would include the ranges for for numbers between 1 and 100, and 100 and 1000. Which is not what we want.

Answer 24

oh. oh wow. i'm so smart...cough thank you very much :D

Answer 25

When I replace the X with the Range I keep ending up with really high numbers

Answer 26

as in?

Answer 27

If the range of the function f(x) = 7x – 2.7 is {14.1, 30.9, 41.4, 58.9, 68}, what is its domain? I tried replacing f(x) with the range and i'm getting huge numbers but all my choices are low decimals

Answer 28

James, they gave you the range and want you to find the domakn. So that means:

f (x) = 14.1

And then we have
f (x) = 7x - 2.7

And plug in the first equation into the second and you get:

14.1 = 7x - 2.7

And you do this for each range they gave you and solve for x

Answer 29

Alright I think I understand now thank you!

Answer 30

It was my pleasure!