## anonymous one year ago If y =12 when x= 6, find x when y=-24

1. anonymous

find a point in a graph?

2. freckles

You would tell whoever gave this question that there isn't enough info.

3. freckles

does y vary directly with x maybe?

4. freckles

does y vary indirectly with x? or you not given anything else?

5. anonymous

yes, i want to know too..

6. anonymous

Write an inverse variation equation that relates x and y. Assume that y varies inversely as x. Then solve.

7. freckles

$y=\frac{k}{x}$

8. freckles

plug in x=6,y=12 to find the constant k

9. freckles

that is the first step then there is another step afterwards

10. anonymous

simplify and substitute

11. anonymous

okay i plugged everything in..

12. freckles

did you find the constant k?

13. freckles

that was the whole point in pluggin in your first part (x,y)=(6,12)

14. freckles

first pair*

15. anonymous

so it'd be -3 ?

16. anonymous

17. anonymous

y=kx 12=k(6) 2=k y=2x -24=2x x=-24/2 x=-12

18. freckles

I think 6(12) isn't -3

19. anonymous

thats not even a choice.

20. freckles

$y=\frac{k}{x} \\ xy=k \\ 6(12) =k$

21. freckles

do you know how to multiply 6 and 12?

22. freckles

if you don't you can think of it as 12+12+12+12+12+12 (the sum of six 12's)

23. anonymous

yes i do thanks but my teacher checked it and she said its right

24. freckles

oh you already did the question?

25. anonymous

i did what you said to start off with but then she emailed me back and set it up

26. freckles

ok so when you said -3 you weren't talking about k you were talking about the for x when y=-24

27. anonymous

yes

28. freckles

$xy=k \\ 6(12)=k \\ 72=k \\ \text{ yeah } k \text{ is 72} \\ xy=72 \text{ replaced } k \text{ with } 72 \\ \\ \text{ now what is } x \text{ when } y=-24 \\ -24x=72$ yep final answer is x=-3 when y=-24