# simple question - approximating a square root

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• Nov 18th 2009, 02:51 PM
ayarfal40
simple question - approximating a square root
how do you approximate the differential of a square root? for example the square root of 23, something thats not as obvious.
• Nov 18th 2009, 03:11 PM
mr fantastic
Quote:

Originally Posted by ayarfal40
how do you approximate the differential of a square root? for example the square root of 23, something thats not as obvious.

$f(x + h) \approx f(x) + h f'(x)$.

For the example you give, $f(x) = \sqrt{x}$, $x = 25$ and $h = -2$.