Maths help

• sir sickolot II

  8 Apr 08, 00:21

  I need to find the value of 'p'

  [(900 -p)^0.5] + 4[(81-p)^0.5] = 50

  I know the answer is 53 plus plus... but i donno how to get it.

   

  thanks in advance!

• eagle

  8 Apr 08, 00:33

  let y = 81 - p

  thus,

  (819 + y)^0.5 + 4y^0.5 = 50
  (819 + y)^0.5 = 50 - 4y^0.5

  square both sides

  819 + y = 2500 - 400 y^0.5 + 16y
  15y  - 400y^0.5 +1681 = 0

  Using formula,

  y^0.5 =  5.23 or 21.44 (reject because y >0, (81-p)^0.5 = y^0.5 => y has to be +ve)

  Thus,

  p = 81 - y = 81 - 5.23^2 = 53.65

• ^tamago^

  8 Apr 08, 01:24

  excellent...
• sir sickolot II

  8 Apr 08, 02:06

  thanks eagle!