Quotient Rule (2 Viewers)

[mtsmahia]

Hi guys,

Can someone please help in solving this Q via the Quotient rule..?

y=3x+1/square root of (x+1)

thanks!!

 

[Live Laugh Love]

Hi guys,

Can someone please help in solving this Q via the Quotient rule..?

y=3x+1/square root of (x+1)

thanks!!

Ok, first, express the bottom as (x+1)^1/2.
Then use y=u/v to differenciate. So, y'=(vu'-uv')/(v^2):
u= 3x+1
v= (x+1)^1/2
u'=3
v'=1/2x1(x+1)^-1/2.
=1/2(x+1)^-1/2.

Then put it into the formula above and it should be right
(Hope I've done it right and helped!)

 

[mtsmahia]

Ok, first, express the bottom as (x+1)^1/2.
Then use y=u/v to differenciate. So, y'=(vu'-uv')/(v^2):
u= 3x+1
v= (x+1)^1/2
u'=3
v'=1/2x1(x+1)^-1/2.
=1/2(x+1)^-1/2.

Then put it into the formula above and it should be right
(Hope I've done it right and helped!)

for some reason the answer says
3x+5/2.square root of(x+1) to the power of 3

 

[kurt.physics]

Hi guys,

Can someone please help in solving this Q via the Quotient rule..?

y=3x+1/square root of (x+1)

thanks!!

 

[mtsmahia]

thanks man..!!

 

[Aquawhite]

As usual kurt, an impecable answer. ^_^ I hope you go well in your 2u exam this year!... I am competing against you ....

 

[duckcowhybrid]

Good answer by Kurt but is there a need for all that setting out. I normally jump straight into the line y' = etc. Why do you need to establish u' and v'?

 

[kurt.physics]

As usual kurt, an impecable answer. ^_^ I hope you go well in your 2u exam this year!... I am competing against you ....

I also hope you go well in your HSC exams this year =)

 

[Sleight_of_Hand]

^ No

 

[Timothy.Siu]

Good answer by Kurt but is there a need for all that setting out. I normally jump straight into the line y' = etc. Why do you need to establish u' and v'?

for other people to see

 

[kurt.physics]

Good answer by Kurt but is there a need for all that setting out. I normally jump straight into the line y' = etc. Why do you need to establish u' and v'?

I personally think that establishing u' and v' is a more "safer" method both as it rules out fewer mistakes which is very important for example if they through in a large quotient rule or product rule its easier to have this step by step reference.

Secondly, it lets the marker know that you understand the step by step nature of those questions, which of course is helpful particularly in the HSC. If you make a silly mistake in an easy 2 mark question than at least you can scab a mark as you have shown you understand the process. You will see it can make all the difference.

Just for exams question 2(a)(iii) in the 2u Maths exam 2008:





The marking guidelines for this question are:

- correct answer 2 marks

- Shows some knowledge of the product rule or equivalent merit 1 mark

 

[kurt.physics]

for other people to see

That too =)

 

[duckcowhybrid]

Yeah hmm it seems like too slow for me. I did it in my exercises, but once I got the hang of it, I stopped. Do not that I set out my first line of substitution in full, so I dont automatically simplify or anything.

 

[Uncle]

i stopped remembering the quotient rule.
pointless.
just a derivation of the product rule in conjunction with the chain rule.
never use the quotient rule in uni, would make integrals look even more like hell than they are and integration by inspection harder.

 

[roar84eighty]

Yeah hmm it seems like too slow for me. I did it in my exercises, but once I got the hang of it, I stopped. Do not that I set out my first line of substitution in full, so I dont automatically simplify or anything.

yeah i doubt kurt will finish his paper (despite his obvious skill in maths) if he wastes his time doing that shit

 

[kurt.physics]

yeah i doubt kurt will finish his paper (despite his obvious skill in maths) if he wastes his time doing that shit

Do you think that marks would be lost if you were to go straight into y' for a quotient rule in the HSC exam?

 

[addikaye03]

Do you think that marks would be lost if you were to go straight into y' for a quotient rule in the HSC exam?

dude, you've already answered your own Q.
Marking Guide Line:-2 marks for correct answer.

The HSC markers don't give a shit if you use u' v' system or just go straight ahead and find dy/dx.

 

[Aquawhite]

You can just say you are going to use the such and such method if you really want to. You don't have to write down the values for v' and u' or even the general equation etc... just put in the data them collect and factorise to get the answer ^_^... saves time and you'll get full marks. For such a simple question, all they reall want is to see a line or two of showing that you used a certain method of calculus to get the answer then the answer.

 

[annabackwards]

dude, you've already answered your own Q.
Marking Guide Line:-2 marks for correct answer.

The HSC markers don't give a shit if you use u' v' system or just go straight ahead and find dy/dx.

You'd have enough time to show all working out in a 2U paper though, there aren't that many questions.

 

[Timothy.Siu]

Do you think that marks would be lost if you were to go straight into y' for a quotient rule in the HSC exam?

no, i've never done that ever