1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Is this possible?

  1. Jan 3, 2007 #1
    1. The problem statement, all variables and given/known data
    If y'=0 and y=1 when x=2, and y''-4=0, find the function.


    2. Relevant equations
    [tex]\frac{dy}{dx}=\int\frac{d^{2}y}{dx^{2}}[/tex]



    3. The attempt at a solution

    I hate posting this because I am pretty sure the solution is easy but I just can't seem to see through this question...

    If y'=0 then there must be no x term in the function f(x)... thus y=C is the only possibility. So then y=1 is the only possibility for the initial conditions given.... And if y''=4 then shouldn't y'=4x+C? :/
     
  2. jcsd
  3. Jan 3, 2007 #2

    radou

    User Avatar
    Homework Helper

    The boundary values are y(2) = 1 and..? What do you mean by y' = 0? For which x is this true?
     
  4. Jan 3, 2007 #3
    Have you tried solving the equation y" - 4 =0, and then applying the initial conditions?

    Remember, they are not the general expression as a function of x; those are values of the function and its derivative at the point x = 2.
     
  5. Jan 3, 2007 #4

    cristo

    User Avatar
    Staff Emeritus
    Science Advisor

    These intial conditions are y'(2)=0 and y(2)=1. You have assumed y'=0 for all x.
     
  6. Jan 3, 2007 #5
    Ahhh okay I was misreading the damned question, :redface:... I kinda thought it was worded funny... Trying to breeze through my homework too fast I guess.

    Sorry! Thanks all, I get it now :-)
     
  7. Jan 3, 2007 #6

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    It didn't occur to you that is y'= 0 for all x, then y" couldn't be 4!:rolleyes:
     
  8. Jan 3, 2007 #7
    Yes I knew it was impossible as well. But I figured that the question was not written wrong, I should have reread the question more carefully but I was in too much of a hurry(was due in like 10 minutes). My appologies.
     
    Last edited: Jan 3, 2007
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Is this possible?
  1. How is this possible? (Replies: 12)

  2. Is it possible? (Replies: 3)

Loading...