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Differential Equations appeared 46 times across 3 years — 5.3% of Mathematics. This question is from Linear Differential Equations.

Year 2026 2025 2024 Total
Questions 13 17 16 46

If for the solution curve y = f(x) of the differential equation (dy)/(dx) + ( x)y = (2 + x)/((1 + 2 x)²), x in ((-π)/(2), (π)/(2)), f((π)/(3)) = √(3)10, then f((π)/(4)) is equal to:

Solution & Explanation

Related Formula

Integrating factor (I.F.) for a linear differential equation (dy)/(dx) + Py = Q:

I.F. = e∫ P dx

General solution:

y · (I.F.) = ∫ Q · (I.F.) dx
Core Logic

Given P = x, compute Integrating Factor:

I.F. = e∫ x dx = eln( x) = x

Set up integrated expression solution layout:

y · x = ∫ (2 + x)/((1 + 2 x)²) · x dx = ∫ (2 x + 1)/(( x + 2)²) · dx
Step 1: Evaluate Integration with Half-Angle Substitutions

Using tangent half-angle substitution t = (x)/(2) transformations simplifies the integral loop structure down to:

y · x = (2)/(t + (3)/(t)) + C

Plugging entry condition parameters f((π)/(3)) = √(3)10 tracking t = 1√(3) explicitly isolates boundary condition constant C: C = 0

Step 2: Calculate Target Point Value

At target query point x = (π)/(4), half-angle parameters scale to t = √(2) - 1:

y · √(2) = 2√(2) - 1 + 3√(2) - 1 = 2(√(2) - 1)6 - 2√(2) y = 4 - √(2)14
Pattern Recognition

When integrating complex rational expressions involving trigonometric values, half-angle substitution methods (t = (x)/(2)) are standard for reducing polynomial degrees.

Chapter Mix

Class 12 Mathematics: Differential Equations

Reference Study Guides

More Differential Equations Previous-Year Questions — Page 5

Q66 jee_main_2025_28_jan_morning Leibniz Rule and Linear Differential Equations
Let for some function y = f(x), ∫₀^x t f(t) dt = x² f(x), x > 0 and f(2) = 3. Then f(6) is equal to: (1) 1 (2) 2 (3) 6 (4) 3
  • A. 1
  • B. 2
  • C. 6
  • D. 3

Solution

Related Formula

Leibniz Rule for differentiating under the integral sign:

(d)/(dx) [ ∫ψ(x)φ(x) f(t) dt ] = f(φ(x))φ^ (x) - f(ψ(x))ψ^ (x)
Core Logic

Differentiate both sides of the integral equation with respect to x:

xf(x) = x² f^ (x) + 2xf(x) -xf(x) = x² f^ (x)
Step 1: Solving the Separable Differential Equation

Separating variables:

∫ (f^ (x))/(f(x)) dx = ∫ -(1)/(x) dx ln |f(x)| = -ln x + ln c f(x) = (c)/(x)
Step 2: Applying Boundary Constraints

Given f(2) = 3:

3 = (c)/(2) c = 6 f(x) = (6)/(x)

Evaluating for x = 6:

f(6) = (6)/(6) = 1
Pattern Recognition

Differentiating integral statements instantly converts complex integral equations into clean, separable differential equations.

Chapter Mix

Class 12 Maths: Differential Equations

Q62 jee_main_2025_03_april_morning Linear Differential Equations
Let g be a differentiable function such that ∫₀xg(t)dt=x-∫₀xtg(t)dt [cite: 568], x≥0 [cite: 569] and let y=y(x) satisfy the differential equation (dy)/(dx) - y x = 2(x+1) x g(x) [cite: 571, 575, 578, 581], xin[0,(π)/(2))[cite: 581]. If y(0)=0 [cite: 579] then y((π)/(3)) is equal to[cite: 582]:
  • A. 2π3√(3)
  • B. (4π)/(3)
  • C. (2π)/(3)
  • D. 4π3√(3)

Solution

Related Formula

Leibniz Integral Rule for differentiation:

ddx(∫₀^x f(t)dt) = f(x)
Core Logic

Differentiate the given integral relation using Leibniz rule [cite: 1344]: ddx[∫₀xg(t)dt] = ddx[x-∫₀xtg(t)dt] [cite: 1344] g(x) = 1 - xg(x) g(x)(1+x) = 1 g(x) = (1)/(1+x) [cite: 1345]

Substitute g(x) into target differential equation configuration [cite: 1346]: dydx - y x = 2(x+1) x · ((1)/(1+x)) = 2 x [cite: 1346]

Step 1: Finding the Integrating Factor

This matches a linear form dydx + P(x)y = Q(x) where P(x) = - x. I.F. = e∫ - x dx = eln| x| = x [cite: 1346]

Write general functional solution template [cite: 1348]: y · x = ∫ (2 x · x) dx = ∫ 2 dx = 2x + C [cite: 1348]

Given boundary condition y(0) = 0 0 = 0 + C C = 0 [cite: 1349]. y(x) = (2x)/( x) = 2x x [cite: 1350]

Step 2: Numeric substitution

Substitute variable parameter values x = (π)/(3) [cite: 1352]: y((π)/(3)) = 2((π)/(3)) ((π)/(3)) = (2π)/(3) · 2 = (4π)/(3) [cite: 1351]

Pattern Recognition

Integral functional definitions are codes for simpler underlying derivatives. Applying Leibniz rule immediately extracts the true variable functions.

Chapter Mix

Class 12 Mathematics: Differential Equations

Q66 jee_main_2025_04_april_evening Linear Differential Equations
If a curve y = y(x) passes through the point (1, (π)/(2)) and satisfies the differential equation (7x⁴ y - e^x cosec y) (dx)/(dy) = x⁵, x ≥ 1, then at x = 2, the value of cosine is:
  • A. 2e² - e64
  • B. 2e² + e64
  • C. 2e² - e128
  • D. 2e² + e128

Solution

Core Logic

Let's rearrange the given differential equation by expressing (dy)/(dx):

x⁵ (dy)/(dx) = 7x⁴ y - e^x y

Dividing both sides by x⁵:

(dy)/(dx) = (7)/(x) y - (e^x)/(x⁵) y

Multiply the entire equation by y to clear denominators:

y (dy)/(dx) - (7)/(x) y = -(e^x)/(x⁵)

This can be transformed into a linear form by substituting t = - y. Then (dt)/(dx) = y (dy)/(dx).

Step 1: Solving the Linear ODE

Substituting t leads to:

(dt)/(dx) + (7)/(x) t = -(e^x)/(x⁵)

This is a standard linear first-order ODE with P(x) = (7)/(x). The Integrating Factor (I.F.) is:

I.F. = e∫ (7)/(x) dx = e7 ln x = x⁷

The general solution is:

t · x⁷ = ∫ (-(e^x)/(x⁵)) · x⁷ dx = -∫ x² e^x dx
Step 2: Evaluating the Integration and Constant

Using integration by parts for ∫ x² e^x dx:

∫ x² e^x dx = x² e^x - 2xe^x + 2e^x

Substituting this back:

- y · x⁷ = -e^x(x² - 2x + 2) + C y · x⁷ = e^x(x² - 2x + 2) - C

Since the curve passes through (1, (π)/(2)):

((π)/(2)) · (1)⁷ = e¹(1² - 2(1) + 2) - C 0 = e(1) - C C = e
Step 3: Calculating cos y at x = 2

Now substitute x = 2 and C = e into our equation block:

y · (2⁷) = e²(2² - 2(2) + 2) - e y · 128 = e²(4 - 4 + 2) - e = 2e² - e y = (2e² - e)/(128)
Pattern Recognition

When trigonometric terms are mixed inside an ODE containing derivative blocks like (dx)/(dy) or (dy)/(dx), check if clearing denominators using y or y reveals a standard substitution path for a Linear ODE.

Chapter Mix

Class 12 Mathematics: Differential Equations

Q58 jee_main_2025_04_april_morning Area Bounded by Curves
Let f [0, ∞) → R be a differentiable function such that f(x) = 1 - 2x + ∫₀^x ex - t f(t) dt for all x in [0, ∞). Then the area of the region bounded by y = f(x) and the coordinate axes is
  • A. √(5)
  • B. (1)/(2)
  • C. √(2)
  • D. 2

Solution

Related Formula

Leibniz Integral Rule for differentiation under integral sign:

ddx(∫φ(x)ψ(x) f(t)dt) = f(ψ(x))ψ'(x) - f(φ(x))φ'(x)
Core Logic

Rewrite equation to isolate the integral kernel:

y = 1 - 2x + e^x ∫₀^x e-t f(t)dt

Differentiating with respect to x using product rule and Leibniz rule:

dydx = -2 + e^x ∫₀^x e-t f(t)dt + e^x · (e-x f(x))

Notice that e^x ∫₀^x e-t f(t)dt = y - (1 - 2x). Substitute this back:

dydx = -2 + [y - 1 + 2x] + y dydx - 2y = 2x - 3
Step 1: Solve Differential Equation

Integrating factor I.F. = e∫ -2 dx = e-2x.

y e-2x = ∫ (2x - 3)e-2xdx = (-(2x - 3))/(2)e-2x - (1)/(2)e-2x + c

From original equation, at x=0, f(0) = 1. Evaluating c:

1 = (3)/(2) - (1)/(2) + c c = 0

Thus, y = -x + 1 x + y = 1.

Step 2: Calculate Area

The boundary line is x + y = 1. The area bounded by this line and coordinate axes is a right triangle with intercepts (1,0) and (0,1):

Area = (1)/(2) × 1 × 1 = (1)/(2)
Pattern Recognition

Integral equations of convolution type (ex-t) always simplify directly into standard linear ordinary differential equations of first or second order when tracking Leibniz rules properly.

Chapter Mix

Class 12 Mathematics: Differential Equations Class 12 Mathematics: Area Under Curves

Q63 jee_main_2025_07_april_evening Linear Differential Equations
Let y = y(x) be the solution of the differential equation (x² + 1)y' - 2xy = (x⁴ + 2x² + 1) x, y(0) = 1. Then ∫₋₃³ y(x) dx is:
  • A. 24
  • B. 36
  • C. 30
  • D. 18

Solution

Related Formula

For a linear differential equation (dy)/(dx) + Py = Q, the Integrating Factor (IF) is defined as:

IF = e∫ P dx
Core Logic

Divide the full differential equation by (x²+1):

(dy)/(dx) - ((2x)/(x²+1))y = ((x²+1)² x)/(x²+1) = (x²+1) x

This is a standard Linear Differential Equation with:

P = -(2x)/(x²+1), Q = (x²+1) x IF = e∫ -(2x)/(x²+1) dx = e-ln(x²+1) = (1)/(x²+1)
Step 1: Solve for General Solution

The solution format is y · IF = ∫ Q · IF dx:

y · (1)/(x²+1) = ∫ (x²+1) x · (1)/(x²+1) dx (y)/(x²+1) = x + c

Using the boundary condition y(0) = 1:

(1)/(0+1) = (0) + c c = 1 y = (x²+1)(sin x + 1)
Step 2: Definite Integration Evaluation

We need to evaluate ∫₋₃³ y dx:

∫₋₃³ (x²+1)(sin x + 1) dx = ∫₋₃³ (x² x + x² + x + 1) dx

By symmetry of odd/even functions over symmetric intervals [-a, a]: ∫₋₃³ x² x dx = 0 (since it is an odd function) ∫₋₃³ x dx = 0 (since it is an odd function)

Thus, we are left with the even components:

∫₋₃³ (x² + 1) dx = 2 ∫₀³ (x² + 1) dx = 2 [ (x³)/(3) + x ]₀³ = 2(9 + 3) = 24
Pattern Recognition

Splitting a symmetric interval integral into odd and even parts immediately simplifies calculations by dropping all odd functions down to zero.

Chapter Mix

Class 12 Mathematics: Differential Equations Class 12 Mathematics: Integral Calculus

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