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

# If Y = 2 X 9 3 − 5 7 X 7 + 6 X 3 − X , Find D Y D X a T X = 1 - Mathematics

$\text{ If } y = \frac{2 x^9}{3} - \frac{5}{7} x^7 + 6 x^3 - x, \text{ find } \frac{dy}{dx} at x = 1 .$

#### Solution

$\frac{dy}{dx} = \frac{d}{dx}\left( \frac{2 x^9}{3} - \frac{5}{7} x^7 + 6 x^3 - x \right)$
$= \frac{2}{3}\frac{d}{dx}\left( x^9 \right) - \frac{5}{7}\frac{d}{dx}\left( x^7 \right) + 6\frac{d}{dx}\left( x^3 \right) - \frac{d}{dx}\left( x \right)$
$= \frac{2}{3}\left( 9 x^8 \right) - \frac{5}{7}\left( 7 x^6 \right) + 6\left( 3 x^2 \right) - 1$
$= 6 x^8 - 5 x^6 + 18 x^2 - 1$
$\frac{dy}{dx} at x = 1:$
$6 \left( 1 \right)^8 - 5 \left( 1 \right)^6 + 18 \left( 1 \right)^2 - 1$
$= 6 - 5 + 18 - 1$
$= 18$

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 30.3 | Q 24 | Page 34