Quotient Rule (1 Viewer)

[Trebla]

I always write u, v, u' and v' when applying the quotient rule as well the u, du, v and du for integration by parts, particularly with a complex problem. I did this mainly because I found it to be a mental pain figuring it out in my head and it doesn't give me the right answer most of the time anyway because I often get the subtraction the wrong way round. By listing them out, it saves me from thinking too much and it pretty much always gave the correct answer when I do exercises and in exams.
It doesn't really waste time, it only takes like 5-10 seconds to write out plus it provides a form of insurance in case the final answer is wrong and also if the answer is suspected to be wrong then at least the list of the u, v, u' and v' can be immediately checked for correctness rather than redoing the whole differentiation in my head.

 

[youngminii]

I find it funny that people are arguing against the person that's easily the best at maths in this whole forum.
Here's an idea: You stick to what you do, kurt will stick to what he does, and we'll see who gets a better HSC mark for Maths.

 

[Brontecat]

I always write u, v, u' and v' when applying the quotient rule as well the u, du, v and du for integration by parts, particularly with a complex problem. I did this mainly because I found it to be a mental pain figuring it out in my head and it doesn't give me the right answer most of the time anyway because I often get the subtraction the wrong way round. By listing them out, it saves me from thinking too much and it pretty much always gave the correct answer when I do exercises and in exams.
It doesn't really waste time, it only takes like 5-10 seconds to write out plus it provides a form of insurance in case the final answer is wrong and also if the answer is suspected to be wrong then at least the list of the u, v, u' and v' can be immediately checked for correctness rather than redoing the whole differentiation in my head.

i do this as well

u= v=
u'= v'=

y'= uv'+vu'

this way the marker can see exactly what i'm doing and hopefully award me marks for correct method - even if i get the answer wrong

 

[addikaye03]

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

Don't be mistaken, i'm not saying that you gotta work fast and take 'shortcuts' to have a plethora of time in 2U. I finished the 2008 in like 1.5 hrs. The rest i used for checking etc.

I always set it out as such:

u= , v=

u'= , v'=

y'=vu'+uv' OR/ y'=vu'-uv'/(v^2)

 

[ninetypercent]

you don't lose marks. Like in the chain rule, you don't lose marks for not saying y = u^5, u = 2x +3. You can jump straight to dy/dx. I prefer to not write out the u and v.