The area (in sq. units) of the region $\mathrm{A}=\left\{(x, y) / \frac{y^2}{2} \leq x \leq y+4\right\}$

The area (in sq. units) of the region $\mathrm{A}=\left\{(x, y) / \frac{y^2}{2} \leq x \leq y+4\right\}$
  1. 30
  2. $\frac{53}{3}$
  3. 16
  4. 18

Solution

Given that $\frac{y^2}{2} \leq x \leq y+4$ $\begin{array}{ll} \therefore \quad & x=\frac{y^2}{2} \text { and } x=y+4 \\ & \frac{y^2}{2}=y+4^2 \\ \therefore \quad & y^2-2 y-8=0 \\ \therefore \quad & y=4 \text { or }-2 \\ & \Rightarrow x=8 \text { or } 2 \end{array}$ $\therefore \quad \mathrm{A}=\int_{-2}^4\left(y+4-\frac{y^2}{2}\right) \mathrm{d} y$ $\begin{aligned} & \therefore \quad \mathrm{A}=\left[\frac{y^2}{2}+4 y-\frac{y^3}{6}\right]_{-2}^4 \\ & \therefore \quad A=\left(8+16-\frac{64}{6}\right)-\left(2-8+\frac{8}{6}\right) \\ & \therefore \quad \mathrm{A}=18 \\ & \end{aligned}$

Asked in: MHT CET 2023 (09 May Shift 1)

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