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.
$$18$$
Answer :
$$18$$
Solution :
Given equation of the curves are for $$y = \sqrt x $$ and $$x = 2y + 3$$ in the first quadrant.
On solving both the equation for $$y$$, we get
$$\eqalign{
& y = \sqrt {2y + 3} \cr
& \Rightarrow {y^2} = 2y + 3 \cr
& \Rightarrow {y^2} - 2y - 3 = 0 \cr
& \Rightarrow {y^2} - 3y + y - 3 = 0 \cr
& \Rightarrow y\left( {y - 3} \right) + 1\left( {y - 3} \right) = 0 \cr
& \Rightarrow \left( {y + 1} \right)\left( {y - 3} \right) = 0 \cr
& \Rightarrow y = - 1,\,\,3 \cr} $$
∴ Required area of shaded region,
$$\eqalign{
& A = \int_0^3 {\left( {2y + 3 - {y^2}} \right)dy} = \left[ {\frac{{2{y^2}}}{2} + 3y - \frac{{{y^3}}}{3}} \right]_0^3 \cr
& = \left[ {\frac{{18}}{2} + 9 - 9 - 0} \right] \cr
& = 9\,{\text{sq}}{\text{. units}} \cr} $$
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-