[ilovemath]

Look at the question attached.

so I know how to solve differential equations but the answer scheme omits the constant when integrating dt
(i.e: integral of 1*dt)

why is this??

[Hazza616]

I think you missed off the question :P

[Obadetona]

There is no attached question, but check here http://www.examsolutions.co.uk/a-lev...xcel/index.php It has video solutions for every paper. (Edexcel)

[ilovemath]

here

[TenOfThem]

(Original post by ilovemath)
Look at the question attached.

so I know how to solve differential equations but the answer scheme omits the constant when integrating dt
(i.e: integral of 1*dt)

why is this??

You only get a constant on one side

Well you get one on both sides but they always combine so you just put it on one side


Either side is fine

[JO53PHS]

You only need to add + c once, and it doesn't matter which side of the equation it is on. The + c terms are both constant terms, so they end up being collected into a single term anyway.

[ilovemath]

(Original post by TenOfThem)
You only get a constant on one side

Well you get one on both sides but they always combine so you just put it on one side


Either side is fine

no they LEFT IT OUT...it was NO WHERE....

look at question (now attached)

[Intriguing Alias]

(Original post by ilovemath)
no they LEFT IT OUT...it was NO WHERE....

look at question (now attached)

You have limits so there's no need for a +c

[TenOfThem]

(Original post by ilovemath)
no they LEFT IT OUT...it was NO WHERE....

look at question (now attached)

no they didn't

it would appear once you finish integrating


It is like, for example



giving



Do you see a need for this to be y+c = ????

[TenOfThem]

(Original post by hassi94)
You have limits so there's no need for a +c

still exists though

[Intriguing Alias]

(Original post by TenOfThem)
still exists though

Yes but that's why they won't write it in the mark scheme.

[ilovemath]

(Original post by TenOfThem)
no they didn't

it would appear once you finish integrating


It is like, for example



giving



Do you see a need for this to be y+c = ????

yes...always put in +c....I am confused

[TenOfThem]

(Original post by hassi94)
Yes but that's why they won't write it in the mark scheme.

no

they haven't written it because you do not include it until you have integrated the second side

[Intriguing Alias]

(Original post by TenOfThem)
no

they haven't written it because you do not include it until you have integrated the second side

Oh sorry I assumed the OP was asking about the next part of the question, and furthermore assuming there was a next part of the question. If she meant why isn't it int(blah) + c then sorry you're right but I didn't know she meant that (if she does).

[TenOfThem]

(Original post by ilovemath)
yes...always put in +c....I am confused

Really?????


So from

You would write



and then you would do



why???????

[ilovemath]

(Original post by TenOfThem)
Really?????


So from

You would write



and then you would do



why???????

no...

dh/(0.4-0.02*sqrt(h)) = dt
therefore
integral dh/(0.4 - 0.02*sqrt(h)) = integral dt

on the LHS the plus c vanishes but on the other side why would it?

[Intriguing Alias]

(Original post by ilovemath)
no...

dh/(0.4-0.02*sqrt(h)) = dt
therefore
integral dh/(0.4 - 0.02*sqrt(h)) = integral dt

on the LHS the plus c vanishes but on the other side why would it?

So you're not talking about putting +c whilst there is still an integral there? Can you link us to the mark scheme so we know what you're asking rather than just guessing?

[ilovemath]

(Original post by hassi94)
So you're not talking about putting +c whilst there is still an integral there? Can you link us to the mark scheme so we know what you're asking rather than just guessing?

here

[Intriguing Alias]

(Original post by ilovemath)
here

So where's the actual problem? Where do you think there should be a +c?

[TenOfThem]

(Original post by hassi94)
So where's the actual problem? Where do you think there should be a +c?

ditto