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Math Help - Definition of a derivative to find....

  1. #1
    Junior Member
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    Definition of a derivative to find....

    \frac{d}{dx} \frac{1}{\sqrt{x}}

    I feel retarded. I know how to find derivatives using the power rule and such but I'm having the hardest time doing this one

    Please help.
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  2. #2
    MHF Contributor

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    It is just algebra.

    \displaystyle<br />
\frac{1}<br />
{{\sqrt {x + h} }} - \frac{1}<br />
{{\sqrt x }} = \frac{{\sqrt x  - \sqrt {x + h} }}<br />
{{\sqrt x \sqrt {x + h} }} = \frac{{ - h}}<br />
{{\sqrt x \sqrt {x + h} \left( {\sqrt x  + \sqrt {x + h} } \right)}}<br />
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