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Math Help - Derivative of Squareroot

  1. #1
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    Derivative of Squareroot

    I need to find the square root of:
     <br />
f(x) = \sqrt{x^2+15}<br />

    The answer I got is:
     <br />
f'(x) = \frac{x}{\sqrt{x^2+15}}<br />

    Is this correct? if not please explain.
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  2. #2
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    the answer is actually: f'(x) = x / 2*(sqrt(x^2+15)

    because: f(x) = (x^2+15)^(1/2)
    so: f'(x) = (1/2)*(x^2+15)^(-1/2)*x <------ the inner derivative
    and finally: f'(x) = x / 2*(sqrt(x^2+15)
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  3. #3
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    wouldn't the inner derivative be 2x? since it was x^2
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  4. #4
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    my bad... your answer was correct...
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  5. #5
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    great...thank you
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