Welcome, Guest. Please login or register.

May 25, 2019, 12:03:36 pm

Author Topic: question  (Read 718 times)  Share 

0 Members and 1 Guest are viewing this topic.

melanie.dee

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 477
  • Respect: +1
question
« on: November 07, 2007, 10:44:53 pm »
0
i cant work out why my answer is wrong, and not what the solutions say. could someone please help me with this question

if y = xloge x/3 - x, find dy/dx

first problem is, i cant work out if the question means xloge(x/3) - x or xloge(x/3 - x)

i did it as though it was the former. and i think the solutions did too, except i cant really follow what they've done. anyway can someone explain the answer to that please

enwiabe

  • Putin
  • ATAR Notes Legend
  • *******
  • Posts: 4424
  • Respect: +527
question
« Reply #1 on: November 07, 2007, 11:06:41 pm »
0
Using the product rule on xlog_e(x/3) and standard differentiation on '-x',

dy/dx = (derivative of 'x' multiplied by log_e(x/3)) + (derivative of log_e(x/3) multiplied by x) - (derivative of x)
 
= 1 x log_e(x/3) + x*(1/3)/(x/3) - 1
= log_e(x/3) + x/x - 1
= log_e(x/3) + 1 - 1
= log_e(x/3)

melanie.dee

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 477
  • Respect: +1
question
« Reply #2 on: November 07, 2007, 11:12:24 pm »
0
thanks argh fuck i realised what i did.. im an idiot. thanks a lot!