# Math Help - simple question - approximating a square root

1. ## 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.

2. 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 $h = -2$.