Why? Amaths Qns

• Nathpoop

  6 May 09, 17:39

  Why is

  lg (x^2y / 1+x) =2

  x^2y / 1+x = 2

  Therefore, y =100(1+x) / x^2

  Can someone help me explain?

  Thanks in adv.

• Forbiddensinner

  6 May 09, 18:11

  Originally posted by Nathpoop:

  Why is

  lg (x^2y / 1+x) =2

  x^2y / 1+x = 2

  Therefore, y =100(1+x) / x^2

  Can someone help me explain?

  Thanks in adv.

  There seems to a mistake at the "x^2y / 1+x = 2" part.

  The workings should be:

  lg ( (x^2)(y)/ 1+x ) = 2

  ((x^2)(y)/ 1+x ) = 10^2

  Hence, y = 100(1+x)/ (x^2)

• Only-Way-4-Destiny!

  6 May 09, 21:24

  Only when both sides are logged then you can remove the logs.

   

  lg (x^2y / 1+x) =2

  x^2y / 1+x = 2    (x)

   

  lg ( (x^2)(y)/ 1+x ) = 2

  ((x^2)(y)/ 1+x ) = 10^2 (correct)

   

• Forbiddensinner

  6 May 09, 22:03

  Originally posted by Only-Way-4-Destiny!:

  Only when both sides are logged then you can remove the logs.

   

  lg (x^2y / 1+x) =2

  x^2y / 1+x = 2    (x)

   

   

  lg ( (x^2)(y)/ 1+x ) = 2

  ((x^2)(y)/ 1+x ) = 10^2 (correct)

   

  I took quite a bit of shortcut :P

  Sorry.