Differentiation Help! (1 Viewer)

[twinklegal19]

I have trouble with this question





Any help is appreciated, thanks!

 

[Bored_of_HSC]

I have trouble with this question, and have no idea where to start...





Any help is appreciated, thanks!

Plug in y, dy/dx and d2y/dx2 and equate coefficients. You can solve from there easily (or it may be messy)

 

[twinklegal19]

plug in y, dy/dx and d2y/dx2 and equate coefficients.

oh oops I totally forgot about that lol, thanks

is there a faster way though? I've done a similar question to this before and I didn't have to sub in anything

EDIT: just subbed everything in but I still don't get how you can find a, b and c :S

 

[nightweaver066]

oh oops I totally forgot about that lol, thanks

is there a faster way though? I've done a similar question to this before and I didn't have to sub in anything

EDIT: just subbed everything in but I still don't get how you can find a, b and c :S

Find dy/dx and d^2y/dx^2

Sub in y and dy/dx in to the differential equation.

Rearrange such that d^2y/dx^2 is on one side and everything else is on the other.

Equate coefficients with d^2y/dx^2 equation.

I haven't tried this yet but it may work.

You could mix things around like subbing in y and d^2y/dx^2, or dy/dx and d^2y/dx^2 to try it out.

 

[Bored_of_HSC]

oh oops I totally forgot about that lol, thanks

is there a faster way though? I've done a similar question to this before and I didn't have to sub in anything

EDIT: just subbed everything in but I still don't get how you can find a, b and c :S

Not sure if there's a faster way :/ (can't see one, but someone else might have oen)

And i'm not sure why it isn't working. Take a pic of your working and post it up?

 

[twinklegal19]

Oh... I think I got it with nightweaver's method, and basically equated the coefficients of x, lnx and the constants, ending up with 3 simultaneous equations.

 

[Bored_of_HSC]

Oh... I think I got it with nightweaver's method, and basically equated the coefficients of x, lnx and the constants, ending up with 3 simultaneous equations.

Nightweavers way was my way lol.

 

[nightweaver066]

Nightweavers way was my way lol.

LOL i was thinking if they were the same but i couldn't really understand it the way you expressed it.

Work on your english m8

 

[twinklegal19]

Nightweavers way was my way lol.

ah sorry!

nightweaver's post was clearer I guess lol

 

[Bored_of_HSC]

LOL i was thinking if they were the same but i couldn't really understand it the way you expressed it.

Work on your english m8

Yeah screw you too lol
But it's more of me being lazy and not wishing to type anything in (i'll be hopeless with latex lol)

 

[twinklegal19]

ok so far I got



hopefully I didn't screw it up...

 

[Bored_of_HSC]

ah sorry!

nightweaver's post was clearer I guess lol

Can't argue there haha.

 

[nightweaver066]

ok so far I got



hopefully I didn't screw it up...

Same equations i got.

 

[RealiseNothing]

ok so far I got



hopefully I didn't screw it up...

That's right.

 

[twinklegal19]

Same equations i got.

That's right.

thanks for your confirmation

so a=4, b=1 and c=3, yay

 

[twinklegal19]

Would rep everyone but... yeah

 

[iBibah]

ok so far I got



hopefully I didn't screw it up...

Yep I got same.

EDIT: lol a bit late again. should have read on to see I had been beaten twice :|

 

[twinklegal19]

Yep I got same.

EDIT: lol a bit late again. should have read on to see I had been beaten twice :|

ah that's ok! Appreciated your time and effort anyway

 

[RealiseNothing]

I'm sure there is an easier way to do this question though.

 

[twinklegal19]

I'm sure there is an easier way to do this question though.

That's what I've been thinking, but I guess a long method is better than no method at all