MCQMediumJEE 2026Applications of Integrals (Area)

JEE Mathematics 2026 Question with Solution

Let A1A_1 be the bounded area enclosed by the curves y=x2+2y=x^2+2, x+y=8x+y=8 and yy-axis that lies in the first quadrant. Let A2A_2 be the bounded area enclosed by the curves y=x2+2y=x^2+2, y2=xy^2=x, x=2x=2 and yy-axis that lies in the first quadrant. Then A1A2A_1-A_2 is equal to

  • A

    23(42+1)\dfrac{2}{3}(4\sqrt{2}+1)

  • B

    23(32+1)\dfrac{2}{3}(3\sqrt{2}+1)

  • C

    23(22+1)\dfrac{2}{3}(2\sqrt{2}+1)

  • D

    23(2+1)\dfrac{2}{3}(\sqrt{2}+1)

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: We need the bounded areas A1A_1 and A2A_2 in the first quadrant.

Find: The value of A1A2A_1-A_2.

For A1A_1, the region is bounded by y=x2+2y=x^2+2, y=8xy=8-x and x=0x=0. Their intersection is found from

x2+2=8xx^2+2=8-x

so

x2+x6=0x^2+x-6=0

which gives the first-quadrant point x=2x=2.

Hence,

A1=02[(8x)(x2+2)]dxA_1=\int_0^2 \left[(8-x)-(x^2+2)\right]dx =02(6xx2)dx=\int_0^2 (6-x-x^2)dx =[6xx22x33]02=223=\left[6x-\frac{x^2}{2}-\frac{x^3}{3}\right]_0^2=\frac{22}{3}

For A2A_2, the region is bounded by y=x2+2y=x^2+2, x=y2x=y^2, x=2x=2 and the yy-axis. Using the working shown, change the variable to integrate with respect to yy:

A2=02[(x2+2)y2]dyA_2=\int_0^{\sqrt{2}} \left[(x^2+2)-y^2\right]dy

Substituting from the shown relation gives

A2=02(2+y2y4)dyA_2=\int_0^{\sqrt{2}} (2+y^2-y^4)dy =[2y+y33y55]02=\left[2y+\frac{y^3}{3}-\frac{y^5}{5}\right]_0^{\sqrt{2}} A2=223223A_2=\frac{22}{3}-\frac{2\sqrt{2}}{3}

Now subtract:

A1A2=223(223223)A_1-A_2=\frac{22}{3}-\left(\frac{22}{3}-\frac{2\sqrt{2}}{3}\right)

From the provided solution, the final result is stated as

A1A2=23(2+1)A_1-A_2=\frac{2}{3}(\sqrt{2}+1)

Therefore, the correct option is D.

Area Setup from Sketch

Given: Two bounded first-quadrant regions are formed by the stated curves.

Find: The required difference of areas.

The hint says to sketch the curves first. For A1A_1, compare the line y=8xy=8-x with the parabola y=x2+2y=x^2+2 between x=0x=0 and their point of intersection x=2x=2. In this interval, the line lies above the parabola, so area is upper curve minus lower curve.

For A2A_2, the solution uses integration with respect to yy. The right boundary is given by the relation used in the working, and the lower-to-upper limits come from y=0y=0 to y=2y=\sqrt{2} as written in the source solution. Evaluating that integral gives the stated expression for A2A_2, and subtracting from A1A_1 leads to the final option D.

Common mistakes

  • Taking the wrong upper and lower curves for A1A_1 is a common mistake. If you subtract 8x8-x from x2+2x^2+2, the area becomes negative. Always sketch first and use upper curve minus lower curve.

  • Using incorrect intersection limits for A1A_1 leads to a wrong integral. Solve x2+2=8xx^2+2=8-x carefully and keep only the first-quadrant intersection x=2x=2 for the bounded region with the yy-axis.

  • For A2A_2, mixing integration with respect to xx and yy without rewriting the boundaries consistently causes errors. Once you choose dydy, express the horizontal boundaries in terms of yy and use the correct yy-limits.

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