JEE Main · Mathematics ↓ Falling

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

Year 2026 2025 2024 Total
Questions 13 17 16 46

The solution curve of the differential equation y(dx)/(dy) = x( ₑ x - ₑ y + 1), x > 0, y > 0 passing through the point (e, 1) is

Solution & Explanation

Core Logic

Given DE: (dx)/(dy) = (x)/(y) (ln((x)/(y)) + 1) Let (x)/(y) = t x = ty. Differentiating w.r.t y:

(dx)/(dy) = t + y(dt)/(dy)
Step 1: Substitution and Integration
t + y(dt)/(dy) = t(ln(t) + 1) = tln t + t y(dt)/(dy) = tln t (dt)/(tln t) = (dy)/(y)

Integrate both sides. Let ln t = p (1)/(t) dt = dp.

∫ (dp)/(p) = ∫ (dy)/(y) ln|p| = ln y + C ln|ln t| = ln y + C ln|ln((x)/(y))| = ln y + C
Step 2: Applying Boundary Conditions

Given curve passes through (e, 1):

ln|ln((e)/(1))| = ln(1) + C C = 0 ln|ln((x)/(y))| = ln y |ln((x)/(y))| = eln y = y
Chapter Mix

Class 12 Maths: Differential Equations

Reference Study Guides

More Differential Equations Previous-Year Questions — Page 10

Q11 jee_main_2024_31_jan_morning Linear Differential Equations
Let y = y(x) be the solution of the differential equation (dy)/(dx) = (( x) + y)/( x( x - x x)), x in (0, (π)/(2)) satisfying the condition y((π)/(4)) = 2. Then, y((π)/(3)) is
  • A. √(3)(2 + ₑ√(3))
  • B. √(3)2(2 + ₑ 3)
  • C. √(3)(1 + 2 ₑ 3)
  • D. √(3)(2 + ₑ 3)

Solution

Core Logic
(dy)/(dx) = (( x)/( x) + y)/( x ((1)/( x) - ( ² x)/( x))) = ( x + y x)/( x (1 - ² x)) (dy)/(dx) = ( x + y x)/( x ² x) = ² x + (2y)/( 2x) (dy)/(dx) - 2 (2x)y = ² x
Step 1: Integrating Factor

This is an LDE of form (dy)/(dx) + Py = Q.

I.F. = e∫ -2 (2x) dx

Let 2x = t 2dx = dt.

I.F. = e-∫ t dt = e-ln| (t/2)| = e-ln| x| = (1)/(| x|)
Step 2: Solution of LDE
y(I.F.) = ∫ Q(I.F.) dx + C y(1)/( x) = ∫ ² x (1)/( x) dx + C

Let x = t ² x dx = dt.

y(1)/( x) = ∫ (dt)/(t) + C = ln| x| + C y = x(ln| x| + C)
Step 3: Boundary Value

Given y(π/4) = 2:

2 = 1(ln 1 + C) C = 2

Thus, y = x (ln| x| + 2). At x = π/3:

y(π/3) = √(3)(ln√(3) + 2)
Chapter Mix

Class 12 Maths: Differential Equations

More Differential Equations Questions — jee_main_2024_31_jan_morning

Practice all Differential Equations previous-year questions →

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%)