Question

The area bounded by the parabolas $$y = {\left( {x + 1} \right)^2}$$   and $$y = {\left( {x - 1} \right)^2}$$   and the line $$y = \frac{1}{4}$$  is-

A. $$4\,{\text{sq}}{\text{.}}\,{\text{units}}$$
B. $$\frac{1}{6} \,{\text{sq}}{\text{.}}\,{\text{units}}$$
C. $$\frac{4}{3} \,{\text{sq}}{\text{.}}\,{\text{units}}$$
D. $$\frac{1}{3} \,{\text{sq}}{\text{.}}\,{\text{units}}$$  
Answer :   $$\frac{1}{3} \,{\text{sq}}{\text{.}}\,{\text{units}}$$
Solution :
The given curves are
$$y = {\left( {x + 1} \right)^2}.....(1)$$
upward parabola with vertex at $$\left( { - 1,\,0} \right)$$  meeting $$y$$-axis at $$\left( {0,\,1} \right)$$
$$y = {\left( {x - 1} \right)^2}.....(2)$$
upward parabola with vertex at $$\left( {1,\,0} \right)$$  meeting $$y$$-axis at $$\left( {1,\,0} \right)$$
$$y = \frac{1}{4}.....(3)$$
a line parallel to $$x$$-axis meeting (1) at $$\left( { - \frac{1}{2},\,\frac{1}{4}} \right),\,\left( { - \frac{3}{2},\,\frac{1}{4}} \right)$$
and meeting (2) at $$\left( {\frac{3}{2},\,\frac{1}{4}} \right),\left( {\frac{1}{2},\,\frac{1}{4}} \right)$$
The graph is as shown
Application of Integration mcq solution image
The required area is the shaded portion given by ar $$\left( {BPCQB} \right) = 2Ar\left( {PQCP} \right)$$       (by symmetry)
$$\eqalign{ & = 2\left[ {\int\limits_0^{\frac{1}{2}} {\left( {{{\left( {x - 1} \right)}^2} - \frac{1}{4}} \right)dx} } \right] \cr & = 2\left[ {\left( {\frac{{{{\left( {x - 1} \right)}^3}}}{3} - \frac{x}{4}} \right)_0^{\frac{1}{2}}} \right] \cr & = 2\left[ {\left( { - \frac{1}{{24}} - \frac{1}{8}} \right) - \left( { - \frac{1}{3}} \right)} \right] \cr & = 2\left[ {\frac{{ - 1 - 3 + 8}}{{24}}} \right] \cr & = \frac{1}{3}{\text{ sq}}{\text{. units}} \cr} $$

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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