MCQMediumJEE 2025Applications of Integrals (Area)

JEE Mathematics 2025 Question with Solution

Let the area of the region {(x,y):2yx2+3,y+x3,yx1}\{(x, y) : 2y \leq x^2 + 3, y + |x| \leq 3, y \geq |x-1| \} be AA. Then 6A6A is equal to:

  • A

    1616

  • B

    1818

  • C

    1414

  • D

    1212

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: The region is defined by

2yx2+32y \leq x^2 + 3 y+x3y + |x| \leq 3 yx1y \geq |x-1|

Find: The value of 6A6A, where AA is the area of the region.

From the inequalities,

yx22+32,y3x,yx1y \leq \frac{x^2}{2} + \frac{3}{2}, \qquad y \leq 3 - |x|, \qquad y \geq |x-1|

The solution notes that the parabola and the lines y=x1y = x-1 and y=1xy = 1-x do not intersect in real points, since

x22+32=x1\frac{x^2}{2} + \frac{3}{2} = x-1

gives discriminant

Δ=410=6\Delta = 4 - 10 = -6

and

x22+32=1x\frac{x^2}{2} + \frac{3}{2} = 1-x

gives

Δ=110=9\Delta = 1 - 10 = -9

So the bounded region is determined effectively by the linear constraints together with the stated inequalities.

Using the split form of the absolute values,

y+x3y + |x| \leq 3

becomes

y3x(x0),y3+x(x<0)y \leq 3-x \quad (x \geq 0), \qquad y \leq 3+x \quad (x < 0)

and

yx1y \geq |x-1|

means the region lies above

y=x1(x1),y=1x(x<1)y = x-1 \quad (x \geq 1), \qquad y = 1-x \quad (x < 1)

Explanation from the extracted solution

The extracted solution states that the area is computed by splitting the region into suitable xx-intervals and evaluating the bounded part using the upper curve

y=min(x22+32,3x)y = \min\left(\frac{x^2}{2}+\frac{3}{2}, 3-|x|\right)

and the lower curve

y=x1y = |x-1|

Final conclusion

According to the solution, the simplified integral gives

A=2A = 2

Hence,

6A=126A = 12

Therefore, the correct option is D.

Common mistakes

  • Taking y+x3y + |x| \leq 3 as only y3xy \leq 3-x for all xx is incorrect because the absolute value must be split into separate cases for x0x \geq 0 and x<0x < 0. Use y3xy \leq 3-|x| or the proper piecewise form.

  • Treating yx1y \geq |x-1| as a single straight line is wrong because x1|x-1| represents two lines. The region must lie above y=1xy = 1-x for x<1x < 1 and above y=x1y = x-1 for x1x \geq 1.

  • Assuming the parabola always forms the boundary without checking intersections can lead to a wrong area. First test where the parabola meets the linear boundaries and determine which upper constraint is actually active in the bounded region.

Practice more Applications of Integrals (Area) questions

Get unlimited AI-adaptive practice, mastery tracking, and an AI tutor that explains every step — free to start.

Related questions