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Maths Question 19 – JEE-MAIN 2026

Let y=y(x) be the solution of the differential equation: dydx+(6x2+(3x2+2x3+4)e2x(x3+2)(2+e2x))y=2+e2x, x(1,2), satisfying y(0)=32. If y(1)=α(2+e2), then α is equal to:

The given differential equation is a first-order linear differential equation of the form dydx+P(x)y=Q(x).

Step 1: Identify and Simplify P(x)✦ Active

The given differential equation is a first-order linear ODE of the form dydx+P(x)y=Q(x). We identify P(x) and simplify it by factoring the numerator:

P(x)=6x2+(3x2+2x3+4)e2x(x3+2)(2+e2x)=3x2(2+e2x)+2e2x(x3+2)(x3+2)(2+e2x) P(x)=3x2x3+2+2e2x2+e2x
Step 2: Calculate Integrating Factor and Solve the ODE○ Expand

Next, we calculate the integrating factor (IF) and solve the differential equation:

P(x)dx=(3x2x3+2+2e2x2+e2x)dx=ln(x3+2)ln(2+e2x)=ln(x3+22+e2x) IF=eP(x)dx=x3+22+e2x The solution is yIF=Q(x)IFdx yx3+22+e2x=(2+e2x)x3+22+e2xdx=(x3+2)dx yx3+22+e2x=x44+2x+C
💡 Teacher's Secret Hint

Remember to handle the absolute values in the logarithm based on the given domain x(1,2).

Step 3: Apply Initial Condition and Find α○ Expand

We use the initial condition y(0)=32 to find the constant C, then evaluate y(1) to determine α:

Substituting x=0,y=32:3203+22+e0=044+2(0)+C3223=CC=1 So, the particular solution is y(x)=2+e2xx3+2(x44+2x+1) For x=1:y(1)=2+e213+2(144+2(1)+1)=2+e23(14+3) y(1)=2+e23(134)=1312(2+e2) Comparing with y(1)=α(2+e2), we find α=1312
💡 Teacher's Secret Hint

Double-check your arithmetic when substituting values and simplifying fractions.

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