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Explain solution RD Sharma class 12 chapter Areas of Bounded Region exercise 20.1 question 16 maths

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Answer:

\frac{27}{2} s q \cdot \text { units }

Hint:

y=1+|x+1|, x=-2, x=3, y=0

Given:

Using integration, find area of region bounded by following curve making a rough sketch      

y=1+|x+1|, x=-2, x=3, y=0

Solution:

We have

        y=1+|x+1|  Intersect  x=-2  at \left ( -2,2 \right ) and x=3 at (3,5)

        y=0 is x-axis

        y=1+|x+1|

        \left\{\begin{array}{cc} 1-(x+1) & x \leq-1 \\ 1+(x+1) & x \geq 1 \\ -x & x \leq-1 \\ x+2 & x \geq 1 \end{array}\right.

Let required area be A since limits on x are given we use horizontal strip to find area

        \begin{aligned} &A=\int_{-2}^{3}|y| d x \\\\ &A=\int_{-2}^{-1}|y| d x+\int_{-1}^{3}|y| d x \\\\ &A=\int_{-2}^{-1}-x d x+\int_{-1}^{3}(x+2) d x \end{aligned}

        \begin{aligned} &A=-\left[\frac{x^{2}}{2}\right]_{-2}^{-1}+\left[\frac{x^{2}}{2}+2 x\right]_{-1}^{3} \\\\ &A=-\left[\frac{1}{2}-\frac{4}{2}\right]+\left[\frac{9}{2}+6-\frac{1}{2}+2\right] \\\\ &A=\frac{3}{2}+8+\frac{8}{2} \end{aligned}

        \begin{aligned} &A=\frac{3}{2}+8+4 \\\\ &A=\frac{27}{2} s q \cdot u n i t \end{aligned} \quad\left[\because \int_{a}^{b} x^{n} d x=\left[\frac{x^{n+1}}{n+1}\right]_{a}^{b}\right]

        

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