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« on: September 24, 2014, 11:04:15 PM »
Firstly, I'd like to apologize for the really ugly notations and equations.. there is the solution! I rewrote it--V.I.
Find the solution of the given initial value problem.
\begin{gather}
y' - 2y = e^{2t},\label{A}\\
y(0) = 2.\label{B}
\end{gather}
First, we need to find the integrating factor, which is $I = e^{\int -2\,dt}= e^{-2t}$
so we multiple the entire equation by I, thus, giving us
$e^{-2t} y' - 2e^{-2t} y = 1$.
We see that the left side of the equation can be rewritten as $[e^{-2t}y]'$
and we see that the right side of the equation is in fact 1
therefore: $[e^{-2t} y]' = 1$
we now take the integral of both sides, giving us: $e^{-2t} y = t + C $ where $C$ is a constant. To find $C$, we substitute $y = 2$ when $t$ = 0 (this information is given in the question). We find out that $C = 2$.
rearranging the formula, we come to the solution as
\begin{equation*}
y = (t+2) e^{2t}.
\end{equation*}