Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 11

# 1 √ X - Mathematics

$\frac{1}{\sqrt{x}}$

#### Solution

$\frac{d}{dx}\left( f(x) \right) = \lim_{h \to 0} \frac{f\left( x + h \right) - f\left( x \right)}{h}$
$= \lim_{h \to 0} \frac{\frac{1}{\sqrt{x + h}} - \frac{1}{\sqrt{x}}}{h}$
$= \lim_{h \to 0} \frac{\sqrt{x} - \sqrt{x + h}}{h\sqrt{x}\sqrt{x + h}} \times \frac{\sqrt{x} + \sqrt{x + h}}{\sqrt{x} + \sqrt{x + h}}$
$= \lim_{h \to 0} \frac{x - x - h}{h\sqrt{x}\sqrt{x + h}\left( \sqrt{x} + \sqrt{x + h} \right)}$
$= \lim_{h \to 0} \frac{- h}{h\sqrt{x}\sqrt{x + h}\left( \sqrt{x} + \sqrt{x + h} \right)}$
$= \lim_{h \to 0} \frac{- 1}{\sqrt{x}\sqrt{x + h}\left( \sqrt{x} + \sqrt{x + h} \right)}$
$= \frac{- 1}{\sqrt{x}\sqrt{x}\left( \sqrt{x} + \sqrt{x} \right)}$
$= \frac{- 1}{x \times 2\sqrt{x}}$
$= \frac{- 1}{2 x^\frac{3}{2}}$
$= - \frac{1}{2} x^\frac{- 3}{2}$


Concept: The Concept of Derivative - Algebra of Derivative of Functions
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#### APPEARS IN

RD Sharma Class 11 Mathematics Textbook
Chapter 30 Derivatives
Exercise 30.2 | Q 1.02 | Page 25