Solve the Differential liquation using separation of variabl
     Solve the Differential liquation using separation of variables: e^x y dy/dx = e^-y + e^-2x - y 
  
  Solution
e^x . y.dy/dx. = e^(-y) + e^(-2x-y)
e^x. y. dy/dx = e^(-y) + e^(-2x) . e^(-y)
e^x. y.dy/dx = e^(-y)[ 1+ e^(-2x)]
Divide by e^x
y.dy/dx = [e^(-y)/e^x]. [1+e^(-2x)]
y.dy/dx = e^(-y).e^(-x).[1+ e^(-2x)]
Divide by e^(-y)
[y/ e^(-y)] .dy/dx = e^(-x). e^(-3x)
y.e^(y).dy/dx = e^(-x). e^(-3x)
y. e^(y).dy = [ e^(-x). e^(-3x)] dx
Taking integration on both sides
INT [ e^y.y.dy = INT [ e^(-x) + e^(-3x)]dx
y.e^y - INT [ e^y].dy = -e^(-x) - (1/3).e^(-3x) + C
y.e^y - e^y = -e^(-x) - (1/3).e^(-3x) +C________ C is constant

