Q40 / 90 · JEE Main 2022 (29 Jul Shift 2) · Mathematics

Let y=yx be the solution curve of the differential equation dydx+2x2+11x+13x3+6x2+11x+6y=x+3x+1,x>-1, which passes through the point 0,1. Then y1 is equal to

  • A
    12
  • Correct answer
    B
    32
  • C
    52
  • D
    72

Solution

Given,

dydx+2x2+11x+13x3+6x2+11x+6y=x+3x+1

Now comparing with dydx+y×px=qx
We get px=2x2+11x+13x3+6x2+11x+6

So IF=e∫2x2+11x+13x3+6x2+11x+6dx

Now finding the integration we get,

∫pxdx=∫2x2+11x+13dxx+1x+2x+3

Using partial fraction we get,

2x2+11x+13x+1x+2x+3=Ax+1+Bx+2+Cx+3

On solving we get A=42=2, B=1 and C=-1

So, ∫pxdx=Alnx+1+Blnx+2+clnx+3

=lnx+12x+2x+3

So, IF=e∫pxdx=x+12x+2x+3

Now solution of differential equation is given by

 y×IF=∫Q×IFdx

⇒y×x+12x+2x+3=∫x+3x+1x+12x+2x+3dx

⇒y×x+12x+2x+3=x33+3x22+2x+c

Now given curve passes through 0,1,

So, ⇒1×0+120+20+3=033+3×022+2×0+c⇒c=23

So, curve becomes y×x+12x+2x+3=x33+3x22+2x+23

Now put x=1 we get, y×1+121+21+3=133+3×122+2×1+23

⇒y×3=1+32+2⇒y×3=92

 ⇒y1=32

Hence, the correct answer is option: 'B'.

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