Mathematics · Differential Equations

JEE Main 2024 — 27 January, Shift 1 — Question 21

If the solution of the differential equation (2x+3y−2)dx+(4x+6y−7)dy=0,y(0)=3(2 x+3 y-2) d x+(4 x+6 y-7) d y=0, y(0)=3 is αx+βy+3log⁡e∣2x+3y−γ∣=6\alpha x+\beta y+3 \log _{e}|2 x+3 y-\gamma|=6, then α+2β+3γ\alpha+2 \beta+3 \gamma is equal to _______\_\_\_\_\_\_\_ .

Answer: 29

Numerical answer — enter this value.

Step-by-step solution

2x+3y−2=t4x+6y−4=2t2 \mathrm{x}+3 \mathrm{y}-2=\mathrm{t} \quad 4 \mathrm{x}+6 \mathrm{y}-4=2 \mathrm{t}

2+3dydx=dtdx4x+6y−7=2t−32+3 \frac{d y}{d x}=\frac{d t}{d x} \quad 4 x+6 y-7=2 t-3

dydx=−(2x+3y−2)4x+6y−7\frac{d y}{d x}=\frac{-(2 x+3 y-2)}{4 x+6 y-7} dtdx=−3t+4t−62t−3=t−62t−3\frac{\mathrm{dt}}{\mathrm{dx}}=\frac{-3 \mathrm{t}+4 \mathrm{t}-6}{2 \mathrm{t}-3}=\frac{\mathrm{t}-6}{2 \mathrm{t}-3}

∫2t−3t−6dt=∫dx\int \frac{2 \mathrm{t}-3}{\mathrm{t}-6} \mathrm{dt}=\int \mathrm{dx}

∫(2t−12t−6+9t−6)⋅dt=x\int\left(\frac{2 \mathrm{t}-12}{\mathrm{t}-6}+\frac{9}{\mathrm{t}-6}\right) \cdot \mathrm{dt}=\mathrm{x}

2t+9ln⁡(t−6)=x+c2 \mathrm{t}+9 \ln (\mathrm{t}-6)=\mathrm{x}+\mathrm{c}

2(2x+3y−2)+9ln⁡(2x+3y−8)=x+c2(2 x+3 y-2)+9 \ln (2 x+3 y-8)=x+c

x=0,y=3x=0, y=3

c=14\mathrm{c}=14

4x+6y−4+9ln⁡(2x+3y−8)=x+144 x+6 y-4+9 \ln (2 x+3 y-8)=x+14

x+2y+3ln⁡(2x+3y−8)=6x+2 y+3 \ln (2 x+3 y-8)=6

α=1,β=2,γ=8\alpha=1, \beta=2, \gamma=8

α+2β+3γ=1+4+24=29\alpha+2 \beta+3 \gamma=1+4+24=29

Answer key and solution verified before publishing.

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Exam
JEE Main 2024
Subject
Mathematics
Chapter
Differential Equations
Topic
Methods of solving a First Order,First Degree Differential