## taranicolee Group Title log-5x=log (10-3x) 2 years ago 2 years ago

1. slaaibak Group Title

$\log (-5x) = \log(10 - 3x)$ Is that the question?

2. taranicolee Group Title

3. slaaibak Group Title

Do you agree that -5x = 10 - 3x ?

4. FoolForMath Group Title

x=-5?

5. taranicolee Group Title

i understand that one now though. but another one of the questions is log a=og(4a-9) and the answer is supposed to be 3 but i'm getting 2.25

6. taranicolee Group Title

yeah -5 is what i got (:

7. slaaibak Group Title

I don't think you can have a negative log tho :/ so no real solutions?

8. FoolForMath Group Title

but RHS is imaginary!

9. taranicolee Group Title

true

10. FoolForMath Group Title

so,no real solution exists.

11. slaaibak Group Title

log a = log(4a - 9) Now: a = 4a - 9 -3a = -9 a = 3

12. taranicolee Group Title

OH dude. i'm dumb. for some reason i was moving it over and changing it to -4a -.- thank you so much !!!!

13. FoolForMath Group Title

you are not dumb,silly mistakes happens :-)

14. taranicolee Group Title

(: thanks !

15. slaaibak Group Title

haha, the mistakes I've made in math are far worse :) Hope this helped!

16. taranicolee Group Title

wait i'm sorry can i ask another question? ( i was absent when this was all being taught) but how would you solve -4log3-9m=-4? since there's no log on the right side of the equation?

17. slaaibak Group Title

$-4\log(3-9m)=-4$ ?

18. taranicolee Group Title

$-4\log _{3}-9m=-4$ (:

19. slaaibak Group Title

wait, that doesn't make sense. $-4\log_3(-9m)=-4$

20. taranicolee Group Title

maybe that's how it's supposed to be. it just doesn't show up like that on the worksheet.

21. slaaibak Group Title

Assuming that's the question: First divide both side by -4: $\log_3(-9m) = 1$ Now, you need to know this property of logarithms: $a^x = b$ $\log_a b = x$ $a^x = b$ Now your problem: $\log_3(-9m) = 1 \rightarrow 3^1 = -9m$ $m={-1 \over 3}$

22. taranicolee Group Title

WOW. you're great.

23. slaaibak Group Title

:) Know the laws by heart, and it will be very very easy!

24. taranicolee Group Title

haha i hope so.