The area of the region bounded by the parabola $(y-2)^2=x-1$, the tangent to the parabola at the point $(2…

The area of the region bounded by the parabola $(y-2)^2=x-1$, the tangent to the parabola at the point $(2,3)$ and the $x$-axis is
  1. 3
  2. 6
  3. 9
  4. 12

Solution

Equation of tangent at $(2,3)$ to $ \begin{aligned} & (y-2)^2=x-1 \text { is } S_1=0 \\ & \Rightarrow x-2 y+4=0 \end{aligned} $ Required Area $=$ Area of $\triangle O C B+$ Area of OAPD - Area of $\triangle P C D$ $ \begin{aligned} & =\frac{1}{2}(4 \times 2)+\int_0^3\left(y^2-4 y+5\right) d y-\frac{1}{2}(1 \times 2) \\ & =4+\left[\frac{y^3}{3}-2 y^2+5 y\right]_0^3-1=4-9-18+15-1 \\ & =28-19=9 \text { sq. units } \end{aligned} $
$ \text { (or) } $ $ \text { Area }=\int_0^3\left(2 y-4-y^2+4 y-5\right) d y=\int_0^3\left(-y^2+6 y-5\right) d y=-\int_0^3(3-y)^2 d y=\left[\frac{(y-3)^3}{3}\right]_0^3=\frac{27}{3}=9 \text { sq.units } $

Asked in: JEE Main 2009

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