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

# If F (X) = |X| + |X−1|, Write the Value of D D X ( F ( X ) ) - Mathematics

If f (x) = |x| + |x−1|, write the value of $\frac{d}{dx}\left( f (x) \right)$

#### Solution

$f\left( x \right) = \left| x \right| + \left| x - 1 \right|$
$\text{ Case }1: x<0 (\therefore x-1<-1<0)$
$\left| x \right| = - x; \left| x - 1 \right| = - \left( x - 1 \right) = - x + 1$
$f\left( x \right) = - x + \left( - x + 1 \right) = - 2x$
$f'\left( x \right) = - 2$
$\text{ Case } 2: 0< x <1 (\therefore x>0 \text{ and } x-1<0)$
$\left| x \right| = x; \left| x - 1 \right| = - \left( x - 1 \right) = 1 - x$
$f\left( x \right) = x + 1 - x = 1$
$f'\left( x \right) = 0$
$\text{ Case } 3: x>1 \therefore x>1>0 \Rightarrow x>0)$
$\left| x \right| = x; \left| x - 1 \right| = x - 1$
$f\left( x \right) = x + x - 1 = 2x - 1$
$f'\left( x \right) = 2$

$f'(x)=\begin{cases}-2, \text{When } x < 0 \\0, \text{When }0 < x <1\\2, \text{When } x >1 \end{cases}$

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
Q 7 | Page 47