## saifoo.khan 3 years ago Logarithms

1. OpenstudyUser

I thought you were soo smart, that you would know them by now. LOL jk jk.

2. saifoo.khan

Lol. I'm not a calculator. I can get stuck too! :P @OpenstudyUser

3. OpenstudyUser

Try distributing.

4. saifoo.khan

$\Large 9^{2x} + 2(9^{x+1}) = 40$ Correction^

5. saifoo.khan

Just tell me the next and step after that please.

6. hartnn

write 9^(x+1) as 9^x.9 then put y=9^x. solve the quadratic

7. saifoo.khan

DANG!!! KILL ME!!!! My teacher told me that. -_- Thanks for recalling @hartnn

8. saifoo.khan

Just guessing, can't we do it like this? $9^{2x} + 2(9^x \times 9) = 40$ Ans so on?

9. saifoo.khan

Next? @micahwood50

10. hartnn

didn't i tell u to do just that?

11. saifoo.khan

Yes, but you said me to write 9^x = y Got that. But can't we solve it by another way? Something like: $9^{2x} + 2(9^x)\times 18=40$

12. hartnn

nopes, i don't think so....no formula for log(a+b) or log (a-b)

13. saifoo.khan

I see. THanks man.

14. saifoo.khan

15. saifoo.khan

@OpenstudyUser kept on distributing. :D

16. OpenstudyUser

I atleast tried -_-

17. micahwood50

Just do what hartnn told you to do.

18. saifoo.khan

I want to learn your method too! @micahwood50

19. micahwood50

My "method" is incorrect. I just though lnab = ln (a + b), but it's actually lna + lnb so forgot it.

20. saifoo.khan

Oh. No problem. Thanks for trying though. :)

21. saifoo.khan

I solved it @hartnn . got: x = 0.315

22. hartnn

what roots of quadratic did u get?

23. saifoo.khan

2, -20

24. hartnn

yup. can't be -20 so 9^x=2 x=0.315 u are correct!

25. saifoo.khan

Yep. Thanks.