Question

The area of the region bounded by the parabola $${\left( {y - 2} \right)^2} = x - 1,$$    the tangent of the parabola at the point $$\left( {2,\,3} \right)$$  and the $$x$$-axis is :

A. 6
B. 9  
C. 12
D. 3
Answer :   9
Solution :
The given parabola is $${\left( {y - 2} \right)^2} = x - 1$$
Vertex $$\left( {1,\,2} \right)$$  and it meets $$x$$-axis at $$\left( {5,\,0} \right)$$
Also it gives $${y^2} - 4y - x + 5 = 0$$
So, that equation of tangent to the parabola at $$\left( {2,\,3} \right)$$  is
$$\eqalign{ & y.3 - 2\left( {y + 3} \right) - \frac{1}{2}\left( {x + 2} \right) + 5 = 0 \cr & {\text{or }}x - 2y + 4 = 0\,\,{\text{which meets }}x{\text{ - axis at }}\left( { - 4,\,0} \right) \cr} $$
Application of Integration mcq solution image
In the figure shaded area is the required area.
Let us draw $$PD$$  perpendicular to $$y$$-axis.
Then required area
$$\eqalign{ & = Ar\left( {\Delta BOA} \right) + Ar\left( {OCPD} \right) - Ar\left( {\Delta APD} \right) \cr & = \frac{1}{2} \times 4 \times 2 + \int_0^3 {x\,dy - \frac{1}{2} \times 2 \times 1} \cr & = 3 + \int_0^3 {{{\left( {y - 2} \right)}^2} + 1\,dy} \cr & = 3 + \left[ {\frac{{{{\left( {y - 2} \right)}^3}}}{3} + y} \right]_0^3 \cr & = 3 + \left[ {\frac{1}{3} + 3 + \frac{8}{3}} \right] \cr & = 3 + 6 \cr & = 9\,{\text{sq}}{\text{. units}} \cr} $$

Releted MCQ Question on
Calculus >> Application of Integration

Releted Question 1

The area bounded by the curves $$y = f\left( x \right),$$   the $$x$$-axis and the ordinates $$x = 1$$  and $$x = b$$  is $$\left( {b - 1} \right)\sin \left( {3b + 4} \right).$$     Then $$f\left( x \right)$$  is-

A. $$\left( {x - 1} \right)\cos \left( {3x + 4} \right)$$
B. $$\sin \,\left( {3x + 4} \right)$$
C. $$\sin \,\left( {3x + 4} \right) + 3\left( {x - 1} \right)\cos \left( {3x + 4} \right)$$
D. none of these
Releted Question 2

The area bounded by the curves $$y = \left| x \right| - 1$$   and $$y = - \left| x \right| + 1$$   is-

A. $$1$$
B. $$2$$
C. $$2\sqrt 2 $$
D. $$4$$
Releted Question 3

The area bounded by the curves $$y = \sqrt x ,\,2y + 3 = x$$    and $$x$$-axis in the 1st quadrant is-

A. $$9$$
B. $$\frac{{27}}{4}$$
C. $$36$$
D. $$18$$
Releted Question 4

The area enclosed between the curves $$y = a{x^2}$$   and $$x = a{y^2}\left( {a > 0} \right)$$    is 1 sq. unit, then the value of $$a$$ is-

A. $$\frac{1}{{\sqrt 3 }}$$
B. $$\frac{1}{2}$$
C. $$1$$
D. $$\frac{1}{3}$$

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