# Stuck on Algebra 1

posted by .

This is kind of like the first question I asked, and I'm still having a little trouble on it.

The Ordered pairs in each exercise are for the same direct variation.
Find the missing value.

(-2,8) and (x,12)

I'm not sure how to work out the problem.

• Stuck on Algebra 1 -

I'm not sure but if i cross multiply the two coordinates, i think the answer is...

x=-3?

• Stuck on Algebra 1 -

Cross-multiplying seems to be the process:
http://www.jiskha.com/display.cgi?id=1199568727

So ...

-2/8 = x/12
8x = -24
x = -3

Right?

• Stuck on Algebra 1 -

yes, x=-3

• Stuck on Algebra 1 -

Although I am sure I will be called on the carpet for saying why, I will try anyway.
If it is a direct variation it is a straight line of form:

y = k x
8 = -2 x
so k = -4
NOW any other point on this line satisfies
y = -4 x
so put in 12 for y
12 = -4 x
x = -3 as you know from "cross multiplying"

• Stuck on Algebra 1 -

yes, that's the way I didn't understand how to do before.

• Stuck on Algebra 1 -

By the way, these problems are a special case of direct variation, linear.
The relation could be quadratic, cubic quartic ....
but is always of form y = k x^n
Here so far we are assuming that n = 1

• Stuck on Algebra 1 -

Do you get it now?

• Stuck on Algebra 1 -

Um, i did until you mention the linear part.

• Stuck on Algebra 1 -

Fixing typo and expanding

y = k x
8 = -2 k
solve that for k
so k = -4
NOW any other point on this line satisfies
y = -4 x
so put in 12 for y
12 = -4 x
x = -3 as you know from "cross multiplying"

• Stuck on Algebra 1 -

I do not think you will get direct variation that is quadratic etc in this course or they would have mentioned it. For now assume direct variation means y = k x

• Stuck on Algebra 1 -

Ok , thank you for your help.

## Similar Questions

1. ### Algebra 1

The ordered pairs in each exercise are for the same direct variation. Find the missing value. (3,2) and (6,y) I don't know how to find the missing value ..
2. ### Algebra 1

The ordered pairs in each exersise are for the same direct variation. Find each missing value. (-2,8) and (x,12) (4,y) and ( 16,12)
3. ### Algebra 1

(x,8) and (6,-16) (3,y) and ( 9,15) (2,y) and (10,15) The ordered pairs in each exersise are for the same direct viration. find each missing value.
4. ### Algebra--Help needed!

Does anyone at least slightly understand direct and inverse variation?
5. ### Algebra

Find three ordered pairs (a,b) that satisfy the equation 3a - 5b = 9. So far, I got (3,0). I'm having trouble finding others. Does anyone have suggestions on other easy ways to find ordered pairs besides guess-and-check?
6. ### Algebra 1

As a team we are having trouble coming up with the same ordered pairs for the following 7x+6y=15 and -7x+y=27. We came up with (17,-8) can you show your steps please
7. ### algebra

Please please help, this is like the only thing i am having trouble on right now, and no one my my family knows about this stuff. Any help would be great! (: x 3 6 9 12 f(x) 9 18 27 36 Does this relationship show direct linear variation?
8. ### Algebra worksheet

Hello. My algebra teacher gave me this worksheet last week and everyone had to bring it yesterday and I haven't done it yet. Can someone please help me. He said Friday is the last day or he's going to take away some points. I've been …
9. ### Algebra

I am totally stuck on this question, can some one help?
10. ### algebra

Hi I'm having trouble with this question I don't understand it at all. This is the question: Suppose y varies directly with x, and y = 15 and x = 5. Write a direct variation equation that relates x and y. What is the value of y when …

More Similar Questions