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Mathematics 46 Online
OpenStudy (anonymous):

first order lnear diff eq

OpenStudy (anonymous):

my integrating factor would be x^-2

OpenStudy (anonymous):

@johnweldon1993

OpenStudy (anonymous):

What kind of linear equation is this? \[y'=P(x)y+Q(x)\quad\text{or}\quad y'+P(x)y=Q(x)~~?\]

OpenStudy (anonymous):

I only ask because in your drawing you have two equal signs...

OpenStudy (anonymous):

dy/dx + P(x)y = Q(x)

OpenStudy (anonymous):

no i mean.. dy/dx- 2y/x = x^2 e^x im sorry

OpenStudy (anonymous):

\[\frac{dy}{dx}-\frac{2}{x}y=x^2e^x\] Integrating factor: \[\ln \mu(x)=\int -\frac{2}{x}\,dx~~\implies~~\mu(x)=x^{-2}\] Distributing the IF, you have \[\begin{align*} \frac{1}{x^2}\frac{dy}{dx}-\frac{2}{x^3}y&=e^x\\\\ \frac{d}{dx}\left[\frac{1}{x^2}y\right]&=e^x\\\\ \frac{1}{x^2}y&=\int e^x\,dx\\\\ \frac{1}{x^2}y&=e^x+C\\\\ y&=x^2e^x+Cx^2 \end{align*}\] Knowing that \(y=0\) when \(x=1\), yo can then find a value for \(C\).

OpenStudy (anonymous):

c= 2.72

OpenStudy (anonymous):

c= -2.72

OpenStudy (anonymous):

Right, it's the negative one. Typically, you're better off with the exact form, \(C=-e\).

OpenStudy (anonymous):

yezzz thank you so muccch

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