## EmmaH 3 years ago True or False? Y varies directly with x and y = -9 when x = 3. When y = 27, the value of x is 9. someone PLEASE explain...:(

1. AriPotta

"y varies directly with x" is y = kx. we have to find out what k is. so we substitute -9 for y and 3 for x. -9 = 3k. can you tell me what k equals?

2. EmmaH

ok one sec..

3. EmmaH

-3?

4. EmmaH

oh so its false?

5. AriPotta

yep. so now we can substitute -3 for k and 27 for y to see if x equals 9. 27 = -3x

6. AriPotta

does x = 9?

7. EmmaH

no x=3 it says so in the prob

8. AriPotta

no, that says when x = 3, y = -9. y and x can be any number. k is the only variable that is constant

9. EmmaH

ok sso its false though?

10. EmmaH

*so

11. AriPotta

why do you think it's false? are you just guessing? :/

12. AriPotta

or did you do the math

13. EmmaH

i did the math -9=3k so -9/3=3k/3 k=-3 right o9r am i totaolly off?

14. AriPotta

yea, k = -3, but we're trying to find out what x equals when y = 27

15. EmmaH

x=-9

16. AriPotta

yes! which is not 9. so it's false. good job :)

17. elisichi

EmmaH, k=-3. So, now you substitute it in to check what x is when y=27 27=(-3)x x=-9 Therefore, it is false.

18. EmmaH

yay :) =D :D =)

19. elisichi

Sorry I just realised I came in a little too late

20. EmmaH

thanks guys...wait are you both guys right?

21. elisichi

I'm a girl :D But close enough!

22. EmmaH

hu ....but thanks anyways

23. elisichi

Anytime!

24. AriPotta

i'm a

25. elisichi

hahahahah

26. EmmaH

lolo thats a way of saying it :)

27. AriPotta

:)