Skip to main contentSkip to solution

General solution of the differential equation dydx=ex22+xy\frac{dy}{dx} = e^{\frac{x^2}{2}} + xy is

Solution

✅ Correct Option: 3

Rearranging the equation:

dydx−xy=ex22\frac{dy}{dx} - xy = e^{\frac{x^2}{2}}

This is a first-order linear differential equation of the form dydx+P(x) y=Q(x)\frac{dy}{dx} + P(x)\,y = Q(x), where P(x)=−xP(x) = -x and Q(x)=ex22Q(x) = e^{\frac{x^2}{2}}.


The integrating factor is:

I.F.=e∫P(x) dx=e∫(−x) dx=e−x22\text{I.F.} = e^{\int P(x)\,dx} = e^{\int (-x)\,dx} = e^{-\frac{x^2}{2}}


Using the standard solution formula:

y⋅I.F.=∫Q(x)⋅I.F. dx+Cy \cdot \text{I.F.} = \int Q(x) \cdot \text{I.F.}\,dx + C

y⋅e−x22=∫ex22⋅e−x22 dx+Cy \cdot e^{-\frac{x^2}{2}} = \int e^{\frac{x^2}{2}} \cdot e^{-\frac{x^2}{2}}\,dx + C

Since ex22⋅e−x22=e0=1e^{\frac{x^2}{2}} \cdot e^{-\frac{x^2}{2}} = e^{0} = 1, this simplifies to:

y⋅e−x22=∫1 dx+Cy \cdot e^{-\frac{x^2}{2}} = \int 1\,dx + C

y⋅e−x22=x+Cy \cdot e^{-\frac{x^2}{2}} = x + C


Multiplying both sides by ex22e^{\frac{x^2}{2}}:

y=(x+C) ex22\boxed{y = (x + C)\,e^{\frac{x^2}{2}}}

where CC is an arbitrary constant.

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question