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Differential Equations · Question 9

JEE Main 2026 (Online) 4th April Evening ShiftNumericalMedium📈 Topic in 71% papers+4
1

Let f be a twice differentiable function such that f(x)= 0x (t-x) dt- 0x f(t) t dt, x (- 2, 2 ). Then f'' ( 6 )+12f' (- 6 )+f ( 6 ) is equal to .

Answer

5

Solution

Put u=t-x: 0x (t-x) dt= -x0 u du= [- e u ]-x0= e x

f(x)= e x- 0x f(t) t dt, and f(0)=0

Differentiating: f'(x)=- x-f(x) x

f'(x)+f(x) x=- x (linear), I.F. =e x dx= x

f(x) x=- x x dx=- x+C

f(0)=0 0=-1+C C=1

f(x)= x-1, f'(x)=- x, f''(x)=- x

f'' ( 6 )+12f' (- 6 )+f ( 6 )=- 32+12 12+ 32-1

=5

Answer: 5

JEE Main 2026 (Online) 4th April Evening Shift

Keep practising — Differential Equations

2

If the curve y=f(x) passes through the point (1, e) and satisfies the differential equation dy=y (2+ e x )dx, x>0, then f(e) is equal to :

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3

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4

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7

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10

Let f be a twice differentiable non-negative function such that (f(x))2 = 25 + 0x ((f(t))2 + (f'(t))2 )dt. Then the mean of f( e(1)), f( e(2)), , f( e(625)) is equal to .

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11

If the solution curve y = f(x) of the differential equation (x2 - 4)y' - 2xy + 2x(4 - x2)2 = 0, x > 2, passes through the point (3, 15), then the local maximum value of f is

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