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Mathematics 7 Online
OpenStudy (itz_sid):

Help please

OpenStudy (itz_sid):

Differential Equations. \[\frac{ dp }{ dt }=2\sqrt{pt}\] with y(0) = −1 as the initial value.

OpenStudy (itz_sid):

Here is my work. I messed up somewhere. Could someone please check my work?

OpenStudy (itz_sid):

@random231

OpenStudy (owen3):

You can quickly check wolfram to make sure you have the right 'final' answer.

OpenStudy (itz_sid):

What happened to the 2?

OpenStudy (itz_sid):

Where did the two go?

OpenStudy (owen3):

Oh Sorry. One sec...

OpenStudy (owen3):

\[ \frac{dp}{dt} = 2\sqrt{pt} \\ \, \\ \frac{dp}{dt} = 2\sqrt{p}\sqrt{t} \\ \, \\ \frac{1}{\sqrt p} \frac{dp}{dt} = 2\sqrt{t} \\ \, \\ \int p^{-1/2}~ \frac{dp}{dt} ~dt= 2\int t^{1/2}~dt \\ \, \\ \int p^{-1/2}~ dp= 2\int t^{1/2}~dt \\ \, \\ \frac{ p^{1/2}}{1/2} =2 \frac{t^{3/2}}{3/2} + C \\ \, \\ 2\sqrt p =2 \frac 2 3 t^{3/2}+ C \\ \, \\ \sqrt p = \frac 2 3 t^{3/2}+ C^{*} \\ \, \\ p = \left( \frac 2 3 t^{3/2}+ C \right)^2 \]

OpenStudy (owen3):

you can leave it in the square root form to find C

OpenStudy (owen3):

In your directions you have a mixture of variables. p , t, and y.

OpenStudy (owen3):

Differential Equations. \[\frac{ dp }{ dt }=2\sqrt{pt}\] with y(0) = −1 as the initial value. <--- did you mean p(0) = -1 ?

OpenStudy (itz_sid):

Then would... \[c = \frac{ 3\sqrt{5}-2 }{ 3 }\]

OpenStudy (itz_sid):

Yes i did, sorry

OpenStudy (itz_sid):

@owen3 Oh wait. no i didnt. I looked at at a different problem...

OpenStudy (itz_sid):

p(1)=5

OpenStudy (owen3):

I was going to say, this gives you a non real solution.

OpenStudy (itz_sid):

Haha, sorry

OpenStudy (owen3):

\[ \sqrt p = \frac 2 3 t^{3/2}+ C^{*} \\ \, \\ \sqrt 5 = \frac 2 3 1^{3/2}+ C^{} \\ \, \\ C = \sqrt 5 - \frac 2 3 \]

OpenStudy (owen3):

\[ p = \left( \frac 2 3 t^{3/2}+ \sqrt 5 - \frac 2 3 \right)^2 \]

OpenStudy (itz_sid):

OpenStudy (owen3):

Is it possible they meant \[ \frac{dP}{dt} = 2 \sqrt{ P(t)} \] also that should be capital \[P \]

OpenStudy (itz_sid):

oh okay. haha... thanks.

OpenStudy (itz_sid):

Yes.

OpenStudy (itz_sid):

Could you check something for me real quick though?

OpenStudy (itz_sid):

I watched this video tutorial on a problem of mine, but it wont accept the answer? Did i happen to input it incorrectly?

OpenStudy (itz_sid):

@owen3 See, i got it right :)

OpenStudy (owen3):

You want to solve $$ \frac{dy}{dt} = ky( 1 - y) $$

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