JEE Main · Mathematics → Steady

Application of Integrals appeared 27 times across 3 years — 3.1% of Mathematics. This question is from Area Under Curve.

Year 2026 2025 2024 Total
Questions 9 11 7 27

Let the area of the region (x, y): x²y + 4 ≥ 0, x+2y²≥0, x+4y²≤8, y≥0 be (m)/(n) where m and n are coprime numbers. Then m+n is equal to:

Numerical Answer Type:
Enter a numerical value Answer: 119 to 119 +4 marks

Solution & Explanation

Related Formula
Area = ∫y₁y₂ (xright - xleft) dy
Core Logic

We need to find the area bounded by the curves in the first quadrant (since y ≥ 0). Note that the first inequality x²y + 4 ≥ 0 is trivially satisfied for all x, y ≥ 0. So we focus on bounding x using: Right curve: x = 8 - 4y² Left curve: x = -2y² However, there might be constraints where these cross or hit the axes. We must inspect intersections.

Step 1: Finding Intersection Points

Where do the left and right parabolas intersect? 8 - 4y² = -2y² ⇒ 2y² = 8 ⇒ y² = 4 ⇒ y = 2 (Since y ≥ 0). Wait, does x have boundaries? Since x can't drop arbitrarily into negative territory if it's restricted by other axes. Let's check x²y + 4 ≥ 0. If x = -2y², then y must be bounded, but wait - the question limits are actually split into two regions depending on x²y+4 ≥ 0? Wait, the first inequality x²y+4 ≥ 0 might not be trivial if x is negative. If x = -2y², then (-2y²)² y + 4 ≥ 0 ⇒ 4y⁵ + 4 ≥ 0, which is true for all y ≥ 0. Wait, there seems to be a misinterpretation of the first inequality. Let's look closer at the PDF solution boundaries. The integration is broken at y=1. Why? x+2y² ≥ 0 ⇒ x ≥ -2y². Wait, the solution states another left curve: 2y-4. Is x²y+4 ≥ 0 actually x + 2y - 4 ≥ 0? Yes, OCR shows `x^2y+4` but the solution integrates `(2y-4)`. Thus the original condition is likely x - 2y + 4 ≥ 0 ⇒ x ≥ 2y - 4! Let's assume the left boundary splits between x = -2y² and x = 2y - 4.

Step 2: Region Bounds

Intersection of x = -2y² and x = 2y - 4: -2y² = 2y - 4 ⇒ y² + y - 2 = 0 ⇒ (y+2)(y-1) = 0 ⇒ y = 1. Intersection of x = 2y - 4 and x = 8 - 4y²: 2y - 4 = 8 - 4y² ⇒ 4y² + 2y - 12 = 0 ⇒ 2y² + y - 6 = 0 ⇒ (2y-3)(y+2) = 0 ⇒ y = 3/2. So the region shifts left boundary at y=1 and closes entirely at y=3/2.

Step 3: Setting up the Integration

Region 1 (from y=0 to y=1):

A₁ = ∫₀¹ ((8 - 4y²) - (-2y²)) dy = ∫₀¹ (8 - 2y²) dy A₁ = [ 8y - (2y³)/(3) ]₀¹ = 8 - (2)/(3) = (22)/(3)

Region 2 (from y=1 to y=3/2):

A₂ = ∫₁3/2 ((8 - 4y²) - (2y - 4)) dy = ∫₁3/2 (12 - 2y - 4y²) dy A₂ = [ 12y - y² - (4y³)/(3) ]₁3/2 A₂ = ( 12((3)/(2)) - (9)/(4) - (4)/(3)((27)/(8)) ) - ( 12 - 1 - (4)/(3) ) A₂ = ( 18 - (9)/(4) - (9)/(2) ) - ( 11 - (4)/(3) ) = ( 18 - (27)/(4) ) - (29)/(3) = (45)/(4) - (29)/(3) = (135 - 116)/(12) = (19)/(12)
Step 4: Final Output

Total Area A = A₁ + A₂:

A = (22)/(3) + (19)/(12) = (88 + 19)/(12) = (107)/(12)

This implies m = 107 and n = 12. Since 107 and 12 are coprime, m + n = 107 + 12 = 119.

Pattern Recognition

When dealing with multiple inequalities bounded by y ≥ 0, always project horizontally (integrate wrt y) as the bounds natively trace left-to-right distances. Find intersection nodes to partition the integral correctly.

Chapter Mix

Class 12 Maths: Application of Integrals

Area Under Curve
Area Under Curve

More Application of Integrals Previous-Year Questions — Page 6

Q11 jee_main_2024_31_jan_evening Area Under Curves
The area of the region enclosed by the parabola y = 4x - x² and 3y = (x - 4)² is equal to
  • A. (32)/(9)
  • B. 4
  • C. 6
  • D. (14)/(3)

Solution

Related Formula
Area = ∫ₐb (yupper - ylower) dx
Core Logic

Area Under Curves diagram for Q11 - JEE Main 2024 Evening
Area Under Curves diagram for Q11 - JEE Main 2024 Evening

Find intersection points of y = 4x - x² and 3y = (x - 4)²:

3(4x - x²) = x² - 8x + 16 12x - 3x² = x² - 8x + 16 4x² - 20x + 16 = 0 x² - 5x + 4 = 0

Roots are x = 1, 4.

Area integral:

Area = ∫₁⁴ [ (4x - x²) - ((x - 4)²)/(3) ] dx = [ (4x²)/(2) - (x³)/(3) - ((x - 4)³)/(9) ]₁⁴ = [ 2(16) - (64)/(3) - 0 ] - [ 2(1) - (1)/(3) - ((-3)³)/(9) ] = ( 32 - (64)/(3) ) - ( 2 - (1)/(3) + 3 ) = (32)/(3) - ( 5 - (1)/(3) ) = (32)/(3) - (14)/(3) = (18)/(3) = 6
Chapter Mix

Class 12 Maths: Applications of the Integrals

Q5 jee_main_2024_31_jan_morning Area bounded by Parabolas and Inequalities
The area of the region (x,y): y² ≤ 4x, x < 4, (xy(x - 1)(x - 2))/((x - 3)(x - 4)) > 0, x ≠ 3 is
  • A. (16)/(3)
  • B. (64)/(3)
  • C. (8)/(3)
  • D. (32)/(3)

Solution

Core Logic

Given y² ≤ 4x and x < 4. Analyze the inequality (xy(x-1)(x-2))/((x-3)(x-4)) > 0 considering y > 0 and y < 0 separately.

Area bounded by Parabolas and Inequalities diagram for Q5 - JEE Main 2024 Morning
Area bounded by Parabolas and Inequalities diagram for Q5 - JEE Main 2024 Morning

Step 1: Case I (y > 0)

If y > 0, the inequality reduces to (x(x-1)(x-2))/((x-3)(x-4)) > 0. Using wavy curve method and given x in (0, 4): x in (0, 1) (2, 3).

Step 2: Case II (y < 0)

If y < 0, the inequality reduces to (x(x-1)(x-2))/((x-3)(x-4)) < 0. Using wavy curve method and given x in (0, 4): x in (1, 2) (3, 4).

Step 3: Area Computation

Because the regions map perfectly without overlap in opposite quadrants relative to the x-axis, they form complete parabolic strips when combined: Area = 2 ∫₀⁴ √(x) dx = 2 · (2)/(3)[x3/2]₀⁴ = (4)/(3) · 8 = (32)/(3).

Chapter Mix

Class 12 Maths: Area Under Curves Class 11 Maths: Linear Inequalities

Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)