The Student Room Group

Are 1st order linear differential equations in the general form need to be y always?

Or is y^2 ascpcetiable etc.
Reply 1
Original post by Mihael_Keehl
Or is y^2 ascpcetiable etc.


y' + yf(x) + g(x) =0 only


or perhaps special cases such as
y' + yf(x) +yn g(x) =0, except n=-1, BERNOULLI
y' + f(y)/x +g(y) =0 TREAT x and y THE OTHER WAY ROUND
(edited 8 years ago)
Reply 2
Original post by Mihael_Keehl
Or is y^2 ascpcetiable etc.


It has to be yy, if it's not yy then it's a non-linear DE.
Reply 3
Original post by TeeEm
y' + yf(x) + g(x) =0 only


or perhaps special cases such as
y' + yf(x) +yn g(x) =0, except n=-1, BERNOULLI
y' + xf(y) +g(y) =0 TREAT x and y THE OTHER WAY ROUND


Bernoulli DE's aren't linear. :smile:
Original post by TeeEm
y' + yf(x) + g(x) =0 only



or perhaps special cases such as
y' + yf(x) +yn g(x) =0, except n=-1, BERNOULLI
y' + xf(y) +g(y) =0 TREAT x and y THE OTHER WAY ROUND


Thank you for the reply.

I kind of meant like in this example:

https://www.youtube.com/watch?v=H6EgCc6s5Fc

Mr S leaves his final answer (general solution) in terms of 2y^2 etc. do you not need to isolate y?

Thank you though,
Reply 5
Original post by Mihael_Keehl
Thank you for the reply.

I kind of meant like in this example:

https://www.youtube.com/watch?v=H6EgCc6s5Fc

Mr S leaves his final answer (general solution) in terms of 2y^2 etc. do you not need to isolate y?

Thank you though,


this is a different type of ODE known as homogeneous in x and y
Reply 6
Original post by Mihael_Keehl
Thank you for the reply.

I kind of meant like in this example:

https://www.youtube.com/watch?v=H6EgCc6s5Fc

Mr S leaves his final answer (general solution) in terms of 2y^2 etc. do you not need to isolate y?

Thank you though,


final answer can be any form if one is not specifically asked.

this type of equation however is called homogeneous in x and y
Original post by TeeEm
this is a different type of ODE known as homogeneous in x and y


Original post by TeeEm
final answer can be any form if one is not specifically asked.

this type of equation however is called homogeneous in x and y


Sorry about that, and thanks for your help.

May I ask you in your experience have you found that 1st order des 2nd order des are common in STEP?
Reply 8
Original post by Mihael_Keehl
Sorry about that, and thanks for your help.

May I ask you in your experience have you found that 1st order des 2nd order des are common in STEP?


I have almost no experience in STEP, but former students of mine that have done STEP, said thee is always an ODE in STEP (I think in STEP II)

Nevertheless ODE solving is very important for practical reasons as well as "building tools/building intelligence" reasons
Original post by TeeEm
I have almost no experience in STEP, but former students of mine that have done STEP, said thee is always an ODE in STEP (I think in STEP II)

Nevertheless ODE solving is very important for practical reasons as well as "building tools/building intelligence" reasons


great thank you :smile:

Quick Reply

Latest