Help with taylor polynomial: rearrange as y' = 2x^2 - y^2,

bamptom

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Sep 7, 2008
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14
Hi There,

Below is an answer from one of my assignments. I am trying to understand the answer however i am stuck on the parts as listed below.

I have been through my books and online a thousand time but i just cant get my head around this. Your help will be very much appreciated!

Rearrange to the form
y? = 2x2 ? y2 (1)

and evaluate at x = 0:
y?(0) = ?y2(0) = ?4 .

Differentiate (1): How does this differentiate?
y?? = 4x ? 2yy? (2)

from where
y??(0) = ?2y(0)y?(0) = 16 .

Now differentiate (2):
y??? = 4 ? 2(y?)2 ? 2yy?? (3) And this one also?

from where
y???(0) = 4 ? 2(y?(0))2 ? 2y(0)y??(0) = ?92 .

Differentiate (3):
y???? = ?4y?y?? ? 2y?y?? ? 2yy??? (4) And again?
 
Re: Help with taylor polynomial

OK i get most of it now. Implicit differentiation is the key.

I still cant quite understand how -2(y')^2 differentiates to -4y'y''
 
Re: Help with taylor polynomial

bamptom said:
...

I still cant quite understand how -2(y')^2 differentiates to -4y'y''

...


Chain rule, I believe.

~ Mark :)

 
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