differentiation

• vulpes macrotis mutica

  13 Dec 07, 16:46

  if f{x} = [(x^2)(e^x)]+1
  what is f'{x} = ???
  i worked it out on my own and got (2x)(e^x)
  whereas when i copied it off the board the teacher wrote [(2x)(e^x)+(x^2)(e^x)]
  not sure where she got the +(x^2)(e^x) part from ...
  
  anyone care to explain?
• eagle

  13 Dec 07, 16:48

  x^2 e^x
  2x e^ x + x^2 e^x --> use chain rule
• mecinerada

  14 Dec 07, 13:37

  Originally posted by vulpes macrotis mutica:

  if f{x} = [(x^2)(e^x)]+1
  what is f'{x} = ???
  i worked it out on my own and got (2x)(e^x)
  whereas when i copied it off the board the teacher wrote [(2x)(e^x)+(x^2)(e^x)]
  not sure where she got the +(x^2)(e^x) part from ...
  
  anyone care to explain?

  d(ab)/dx = ab' + ba'
  
  f'(x)=(e^x)x^2 + 2x(e^x)