Find the general solution of the differential equations
`(dy)/(dx)+3y=e^(-2x)`

Explanation

`dy/dx + 1.y = 1/(1+e^2x)`.


`I.F. = e^ integ.of 1.dx. = e^x`.


Thus, `y.e^x = integ.of e^x/{1+(e^x)^2}.dx. , [let e^x = tanp , e^x.dx = sec^2 p.dp`. ]


or, `y.e^x = integ.of sec^2 p.dp/(1+tan^2 p). = integ.of dp`.


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