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Mathematics 17 Online
OpenStudy (anonymous):

Solve differential equation- 2 parts. Calculus II

OpenStudy (anonymous):

zepdrix (zepdrix):

Hmm ok so this is separable. Separating the t's and y's gives us,\[\large y^{-4}\;dy=t^{5/2}\;dt\] What part are you having trouble with? :O

OpenStudy (anonymous):

well when I solve for y = all I get is 0.

zepdrix (zepdrix):

Hmmm that's strange +_+ Lemme show ya a few steps, maybe you can see where you went wrong.

zepdrix (zepdrix):

Integrating both sides, we'll apply the `Power Rule for Integration`,\[\large \int\limits y^{-4}\;dy=\int\limits t^{5/2}\;dt\]Giving us,\[\large -\frac{1}{3}y^{-3}=\frac{2}{7}t^{7/2}+C\]

zepdrix (zepdrix):

Any part of that super confusing?

OpenStudy (anonymous):

no not yet lol

zepdrix (zepdrix):

Multiplying both sides by -3 gives us,\[\large y^{-3}=C-\frac{6}{7}t^{7/2}\]And thennnn we want to take the reciprocal of both sides to deal with the negative exponent,\[\large y^3=\frac{1}{C-\dfrac{6}{7}t^{7/2}}\]

zepdrix (zepdrix):

Then take the cube root of both sides, and tada! We have our general solution. I'm not sure how you're coming up with zero +_+ Hmm

OpenStudy (anonymous):

for y=?

OpenStudy (anonymous):

for a constant solution

zepdrix (zepdrix):

Constant solutions...? :\

OpenStudy (anonymous):

hmm...

zepdrix (zepdrix):

Well we figured out part B at least. Hmm

OpenStudy (anonymous):

Constant solutions mean \(y=C\) i.e. \(\frac{dy}{dt}=0\). Observe this reduces our equation to:$$0=t^{5/2}y^4$$since \(t\) is allowed to vary we conclude \(y^4=0\) and therefore \(y=0\) is our only constant solution.

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