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!

Related Rates

  1. Oct 4, 2007 #1
    1. The problem statement, all variables and given/known data
    Suppose that Y=2((x^2)-3x) and dx/dt = 2
    Find dy/dt when x=3

    2. Relevant equations
    the only calc is taking the derivative of the equation, i am wondering if i am doing the whole problem right.

    3. The attempt at a solution
    dy/dx = 4x-6
    find the equation for x=3 and multiply in 2 for the rate of change of time

    I think my answer goes back to the clac. I don't know what number i am supposed to plug in for X, i know it has to do when what X equals at dy/dt and the rate of chage of X over time.
  2. jcsd
  3. Oct 4, 2007 #2


    User Avatar
    Science Advisor
    Homework Helper

    You found
    (The derivative with respect to [itex]x[/itex] when [itex]x=3[/itex].)

    The problem is asking for
    (The derivative with respect to [itex]t[/itex].)
  4. Oct 5, 2007 #3


    User Avatar
    Staff Emeritus
    Science Advisor

    The problem SAYS "Find dy/dt when x= 3"!! What value of x do you think you should put in? The phrase "what x equals at dy/dt" is meaningless.
  5. Oct 5, 2007 #4
    i understand that 3 must be replaced for x, but where does the dx/dt = 2 fit into the equation? I am guessing around somewhere around the radius portion of the equation
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Related Rates
  1. Related rates formula (Replies: 3)

  2. Related Rates (Replies: 2)