1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

d/dx(-4.9x^2+14.7x) | x=2 (I get -19.6 m/s instead of -4.9)

Discussion in 'Mathematics and Physics' started by ElectroNewby, Sep 8, 2014.

  1. ElectroNewby

    ElectroNewby Member

    Joined:
    Jul 20, 2010
    Messages:
    207
    Likes:
    0
    Location:
    Saguenay, Quebec.
    I'm having a hard time figuring this because it seems like I followed every step correctly.
    I get to -4.9 with my calculator

    Edit: not so correctly... see my 2nd post
     
    Last edited: Sep 8, 2014
  2. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

    Joined:
    Oct 30, 2010
    Messages:
    9,908
    Likes:
    1,094
    I get 4.9 too; 2*-4.9+14.7 ; I haven't done it the hard way in quite a while.
     
  3. ElectroNewby

    ElectroNewby Member

    Joined:
    Jul 20, 2010
    Messages:
    207
    Likes:
    0
    Location:
    Saguenay, Quebec.
    Somebody pointed me my error :

    I forgot to add the (x+dx) when replacing t (for y2) in the 14,7t part

    Sorry for bothering for nothing !!
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. MrAl

    MrAl Well-Known Member Most Helpful Member

    Joined:
    Sep 7, 2008
    Messages:
    11,026
    Likes:
    951
    Location:
    NJ

    Hello,

    The derivative is 14.7-9.8*x, evaluated at x=2 we get -4.9 that's all there is to it.
    There's no 't' in your original equation.
     
    • Agree Agree x 1

Share This Page