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Homework Help: Why are they taking the derivative of 1 - x?

  1. Jun 29, 2012 #1
    1. The problem statement, all variables and given/known data
    I'm trying to take the derivative of f(x) = 4 / sqrt(1 - x).

    Normally if I have trouble I just plug my problem into Wolfram Alpha, and it saves the day.

    2. Relevant equations
    However, I don't know why it takes the derivative of 1 - x in the numerator after using the chain rule on 1 / sqrt(1 - x) here:


    3. The attempt at a solution
    I'll say that I understand everything up until the aforementioned point in the problem.
  2. jcsd
  3. Jun 29, 2012 #2


    Staff: Mentor

    Because they're using the chain rule.
    d/dx(1/√u) = d/du(1/√u) * du/dx
  4. Jun 29, 2012 #3
    Ah! It took me awhile, but I finally see what they're doing. Thanks.
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