Question

@kayders1997 Explaining this to me

Answer 1

I think it's C.-48

Answer 2

So you still have xk=y so what would you plug into those values for the first part?

Answer 3

It'd be so much more helpful if you'd explain your reasoning instead of saying, "I think it's c."

kayders1997 is correct in bringing up the formula for direct variation, y=kx. Thank you.

Answer 4

Actually, I'm not sure why I think it's C. :0

We would plug in -4, and 12, right?

Answer 5

No -4K=? what's the other value that corresponds to that part

Answer 6

Ms-Brains: Think back to what we've done before. Apply what you've learned earlier. How did we find the value of k earlier? Do the same thing here.

What is k?

Then, what is the whole "direct variation" equation?

Answer 7

24 or 12?

Answer 8

k=12?

Answer 9

Because it says f(x)=24 when x is-4 were going to use 24 the others number is for the next part

Answer 10

Y=24 x=4 you have to put that into the equation xk=y

Answer 11

(4)12=24 <---like that?

Answer 12

No we don't know k because they don't give it to us in and -4 my bad but otherwise it looks good

Answer 13

We're trying to find k

Answer 14

-24 = 24
k=-2

Answer 15

No x=-4 y=24 put it into equation xk=24 -4(k)=24 do you understand where these numbers come from?

Answer 16

We would plug in -4, and 12, right?

No. Instead, plug in x=-4 and y=24 in y=kx. Find k.

Answer 17

y = k x

Let x=-4 and y=24.

Find k.

Now write y = k x, this time including the value for k that you've just found.

Answer 18

24=(x)-4 <- like this?

Answer 19

X is -4 so kinda close

Answer 20

The 24 is right though

Answer 21

You appear to be subtracting. There is no subtraction in this problem. Fix your equation, please.

Answer 22

Rememeber were trying to find k

Answer 23

"kinda close" doesn't work here. We need to be exact.

Answer 24

You gotta have some positivity not everyone gets things in a fast rate

Answer 25

Making mistakes is the best way to learn what you are doing wrong

Answer 26

if not subtraction, what are we using? multiplication?

Answer 27

Yes

Answer 28

Xk that's multiplication just like 3(2) mutliplication

Answer 29

y = k x involves only multiplication. No subtraction.

You could fix your equation by inserting parentheses in the proper places.

Answer 30

24=(x)-4 <- like this?

Answer 31

24=(k)*4 Okay, so we have the equation. Now what?

Answer 32

-4 for x though now solve for k by?

Answer 33

y = k x
Here, x=-4 and y=+24.
Find k.
k will be negative.

Answer 34

How would you get rid of -4K to just get k alone?

Answer 35

Or what times -4 is 24 another way to think of it

Answer 36

Model:
y = k x

Values of x and y: x=(-4) and y=+24

Substitute these values into y = k x now. Then we'll solve the resulting equation for k.

Answer 37

24=(-6)*-4
24=24
So -6 is the correct answer?

Answer 38

Yes. But would you follow the plan I suggested a minute ago?

+24 = K ( ? )

Answer 39

Yeah that the first part now we have to plug in the 12 for x so we know k is -6 so plug in values for k and x Kx=y and what does y end up being?

Answer 40

-6 isn't the final answer?

Answer 41

No because it's asking what is y when x=12 for the second part by k is -6

Answer 42

But

Answer 43

Indeed it is not; you have to find the proportionality constant, k, first. k = -6.

Now write out the direct variation formula including this k = -6.

Answer 44

So all you have to do it plug in the numbers you know k=-6 x=12
Xk=y what is y?

Answer 45

And that will be your answer :)

Answer 46

24(12)-6 write the final formula like this..

Answer 47

What do you plug in for x and k?

Answer 48

In summary:

1. Use the given info to find the proportionality constant, k. It's -6.
2. Write out the complete equation for direct variation that applies here. Because k = -6, it is y = -6x

3. Now, in a particular case, where another x is given, find the resulting y value.

Answer 49

24 is not in this

Answer 50

12(-6)
X(k)

Answer 51

Thank you for showing your work: 24(12)-6 write the final formula like this..

Actually, the final formula (not the final answer) is y = -6x.

Let x=12 (a particular x-value). Subst. 12 for x in the above equation and calculate y.

Answer 52

X=12 k=-6

Answer 53

Alright. so the final answer is -72.
Thank you both for teaching me how to do it. ^-^ You guys rock!

Answer 54

You're welcome. Yes, when x = 12, y = -72. Very good.