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NCERT Class XII Mathematics Chapter - - Solutions

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Exercise - 7.11
By using the properties of definite integrals, evaluate the integrals in Exercises 208 to 225.
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Question : 224 of 271
Marks: +1, -0
∫04∣x−1∣dx\int\limits_{0}^{4}\left|x-1\right|dx
Solution:  
Let I=∫04∣x−1∣dxI=\int\limits_{0}^{4}\left|x-1\right|dx
Define ∣x−1∣={−(x−1),if (x−1)<0 or x<1x−1,if (x−1)≥0 or x≥1\left|x-1\right| = \begin{cases} -(x-1), & \text{if } (x-1) < 0 \text{ or } x < 1 \\ x-1, & \text{if } (x-1) \ge 0 \text{ or } x \ge 1 \end{cases}
∴I=−∫01(x−1)dx+∫14(x−1)dx\therefore I = -\int\limits_{0}^{1}(x-1)dx + \int\limits_{1}^{4}(x-1)dx =−[(x−1)22]01+[(x−1)22]14=-\left[\frac{(x-1)^2}{2}\right]_{0}^{1}+\left[\frac{(x-1)^2}{2}\right]_{1}^{4}
=−12[0−1]+12[9−0]=-\frac{1}{2}[0-1]+\frac{1}{2}[9-0]
=12+92=5=\frac{1}{2}+\frac{9}{2}=5
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