3
$\begingroup$

The given question is: $$ dy/dt + 2y = 1\ ;\qquad y(0)= 5/2 $$ when i solve this i get $\ln(-4)=c$ now the problem is how to solve $\ln(-4)$?

  • 1
    You must have made some mistake. (The general solution is $y(t)=1/2 + Ae^{-2t}$. No need to take any logarithms to determine $A$.)2011-04-09
  • 1
    The mistake you probably made is that the integral $\int \frac{du}{u}$ is not $\ln (u)+C$; it is $\ln |u|+C$.2011-04-09
  • 0
    @user9176: When working strictly in real numbers at least. All of the other answers here seem way too involved for such a simple problem.2011-07-08

4 Answers 4