## natnatwebb 2 years ago Okay I'm almost there but the answer I'm getting is incorrect.

1. natnatwebb

$\ln (x)+\ln (x-2)=\ln 8$

2. natnatwebb

then...$\ln (x)(x-2)=\ln 8$

3. natnatwebb

then...$\ln (x ^{2}-2x)=\ln 8$

4. natnatwebb

then drop the ln... $x^{2}-2x=8$

5. gohangoku58

going good...

6. RyanL.

well you e^ both sides. That's how the ln cancel. But then you are left with a quadratic equation

7. natnatwebb

split the two, $x^{2}=8$ and $-2x=8$

8. gohangoku58

thats incorrect

9. Jerry123gnzcraft

true ok ok

10. gohangoku58

11. Jerry123gnzcraft

yup

12. gohangoku58

Compare your quadratic equation with $$ax^2+bx+c=0$$ find a,b,c then the two roots of x are: $$\huge{x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}}$$

13. gohangoku58

x^2-2x-8=0

14. natnatwebb

okay gimme a second to work that out.

15. gohangoku58

sure.

16. freewilly922

*** and need to remember to check for valid values of x. if you are taking ln(x) and ln(x-2) what can't x be?

17. RyanL.

You can always complete the square. That's another way of solving this without the long work of using the quadratic

18. natnatwebb

2

19. natnatwebb

whats finishing the square? Sounds like a shortcut I was denied...

20. Jerry123gnzcraft

granted

21. gohangoku58

shortcut only if u have some prsctice.... u wanna learn that ?

22. freewilly922

... or just factor? $x^2-2x-8=0=(x-?)(x+?)$

23. Jerry123gnzcraft

practice some more then use that form

24. gohangoku58

factoring is best here..

25. gohangoku58

can u factor ?

26. natnatwebb

I'll give it a shot! :)

27. gohangoku58

sure do :)

28. Jerry123gnzcraft

go han!!!! go ku!!!! dominate the problem TEAMWORKKKK

29. gohangoku58

? jerry ?

30. Jerry123gnzcraft

GO HAN GO KU

31. RyanL.

$x^2−2x−8=0=(x−A)(x+B)\\ A*B=-8\\ A+B=-2$ Find A and B

32. natnatwebb

Almost there....

33. RyanL.

You have a system of question where you can simply plug in one equation to another if you can't see it right away. Then solve for the missing variable.

34. natnatwebb

its (x-4)(x+2)

35. gohangoku58

thats correct :)

36. gohangoku58

so what are 2 values of x u got ?

37. natnatwebb

ten solving its 4 and -2

38. RyanL.

$(x-4)(x+2)=0$

39. natnatwebb

and -2 would be extraneous

40. gohangoku58

but can x be -2 ?? think ....

41. gohangoku58

yes, so x is only = ?

42. natnatwebb

4?

43. gohangoku58

yup, u got it :)

44. natnatwebb

HAZUAHH!

45. natnatwebb

THanks everyone! I really appreciate it! :)

46. gohangoku58

welcome ^_^