Find the area bounded by the curve , x = 2y + 3 in the first quadrant and x-axis

y = √x


Squaring both sides


y2 = x


In y2 = x parabola it is not defined for negative values of x hence the parabola will be to the right of Y-axis passing through (0, 0)


But we have to plot y = √x which means x,y both can only be positive hence the graph has to be only in 1st quadrant


Hence y = √x will be part of parabola y2 = x only above X-axis in 1st quadrant


(why can’t y be negative? Because the symbol square root itself denotes primary root which means positive root)


x = 2y + 3 is a straight line


To get the intersection points of the straight line and the parabola solve the parabola equation and straight line equation simultaneously


Put x = 2y + 3 in y2 = x


y2 = 2y + 3


y2 – 2y – 3 = 0


y2 – 3y + y – 3 = 0


y(y – 3) + 1(y – 3) = 0


(y + 1)(y – 3) = 0


y = -1 and y = 3


Put y = 3 in y2 = x


x = 32


x = 9


y = -1 doesn’t matter because we are in 1st quadrant


Hence the parabola and straight line intersects at (9, 3)


Plot roughly the parabola and the line and the required area is the shaded region as shown



The point of intersection of straight line with X-axis can be calculated by putting y = 0 in line equation


x = 2(0) + 3 x = 3


Observe that


area bounded = area under y = √x – area under straight line …(i)



Let us fling area under y = √x


Integrate from 0 to 9









Now area under the straight line x = 2y + 3



Integrate from 3 to 9


(why 3 to 9? Because the line cuts X-axis at 3 and the curve y = √x at 9)









Using (i)


area bounded = 18 – 9 = 9 unit2


Hence area bounded by curve and straight line is 9 unit2


15