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Math Help - NEW USER NEED SUM HELP with this calculus prob. Derivative Prob.

  1. #1
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    NEW USER NEED SUM HELP with this calculus prob. Derivative Prob.

    hi im jhay from.. phl. civil engr. student .. first time to take calculus..
    can u explain to me step by step of finding the derivative of a function x√(x-1) using four step rule .. big tnx in advance..
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  2. #2
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    Re: NEW USER NEED SUM HELP with this calculus prob. Derivative Prob.

    I don't know what you mean by the "four step rule". It is a product of two functions, so use the product rule. The second function also needs the use of the chain rule.
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    Re: NEW USER NEED SUM HELP with this calculus prob. Derivative Prob.

    I think these are the four steps that iamjhay is talking about:

    1. Write f(x+h) and f(x)

    2. Compute f(x+h) - f(x)

    3. Simplify \frac{f(x+h)-f(x)}{h}

    4. Find \lim_{h\to0}\frac{f(x+h)-f(x)}{h}

    We would call it computing the derivative from the definition.

    To iamjhay: I think this identity will get you over the difficult part:

    \sqrt{a}-\sqrt{b}=\frac{a-b}{\sqrt{a}+\sqrt{b}}

    If you're still having trouble, show us the work you've done so far and we'll help you with the next step.

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