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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

Let y = y(x) be the solution of the differential equation x (dy)/(dx) - y = x² x, x in (0, π). If y((π)/(2))=(π)/(2), then 6y((π)/(6))-8y((π)/(4)) is equal to :

Solution & Explanation

Related Formula
d((y)/(x)) = (x dy - y dx)/(x²)
Core Logic

Rewrite the differential equation:

x dy - y dx = x² x dx

Divide by x² to create an exact differential:

(x dy - y dx)/(x²) = x dx d((y)/(x)) = x dx
Execution

Integrate both sides:

∫ d((y)/(x)) = ∫ x dx (y)/(x) = ln| x| + C

Given y((π)/(2)) = (π)/(2):

(π/2)/(π/2) = ln| (π)/(2)| + C ⇒ 1 = 0 + C ⇒ C = 1

Equation of curve: y = x(ln| x| + 1)

Evaluate at limits: y((π)/(6)) = (π)/(6)(ln(1)/(2) + 1) = (π)/(6)(-ln 2 + 1) y((π)/(4)) = (π)/(4)(ln 1√(2) + 1) = (π)/(4)(-(1)/(2)ln 2 + 1)

Calculate 6y((π)/(6)) - 8y((π)/(4)):

= 6[(π)/(6)(-ln 2 + 1)] - 8[(π)/(4)(-(1)/(2)ln 2 + 1)] = π(-ln 2 + 1) - 2π(-(1)/(2)ln 2 + 1) = -πln 2 + π + πln 2 - 2π = -π
Pattern Recognition

Whenever you see x dy - y dx, immediately test division by x², y², or xy to convert it directly into exact differential forms like d(y/x) or d(x/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_2026_28_january_evening

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