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Stationary points and nature of calculus question, please help! (2 Viewers)

SpiralFlex

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Oh that brings me to another question. Which textbook would you recommend, Cambridge or Fitzpatrick for Mathematics 2 unit?

I just started year 12 Calculus, so i'm still a little fuzzy, as they say, about some concepts. :)

Thanks again guys!
Cambridge to start Year 12 Calculus. To learn the theory that is. Although people say Fitzpatrick. I like Cambridge better. I highly recommend starting from Chapter 10A.
 
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I might also warn you that when using the FIRST DERIVATIVE TABLE you must actually get NUMERICAL VALUES for the dy/dx row. The maths dept was advised by the BOS a few months ago about this. They no longer accept +/- in the table as you can just put +/- from the question. Ie. If they say: Prove it is a maximum. You can just put + _ - without doing anything. You must actually put numerical values to support your argument!

Otherwise you will loose marks!
 

OldMathsGuy

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Cambridge to start Year 12 Calculus. To learn the theory that is. Although people say Fitzpatrick. I like Cambridge better. I highly recommend starting from Chapter 10A.
I think there's an interesting proviso here for a lot of 2U students. Cambridge is without doubt the best textbook there is covering the 2U and 3U syllabi, and easily the best for preparing good Ext1 Y11 students for the Ext2 course in Y12. For the average 2U student though, I have found that Cambridge can be both daunting as well as confusing if not given solid direction by a teacher or tutor (or perhaps the excellent advice of SpiralFlex if you can be guided by his various postings). Even though the pure 2U Cambridge book scales things back a little and the more recent Y12 2nd ed. book comes with revision exercises, I would certainly suggest Fitzpatrick as perhaps the main book with Cambridge used for extension or alternative explanations/examples/questions. The much maligned Maths in Focus book by Margaret Grove actually has clear explanations and examples and so can surprisingly be of some use. However the main problem with Grove is the standard exercises are tepid at best and the challenge exercises while difficult upon occasion lack relevance to the eventual HSC exam. As such, a pastiche of all three may be the best solution for the dedicated but self-directed 2U student.

Best Regards
OldMathsGuy
 

Drongoski

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I might also warn you that when using the FIRST DERIVATIVE TABLE you must actually get NUMERICAL VALUES for the dy/dx row. The maths dept was advised by the BOS a few months ago about this. They no longer accept +/- in the table as you can just put +/- from the question. Ie. If they say: Prove it is a maximum. You can just put + _ - without doing anything. You must actually put numerical values to support your argument!

Otherwise you will loose marks!
Most unfortunate and can be unfair. With dy/dx in factored form we should only need to investigate the signs of the factors without actually evaluating it, as that can be time-consuming and strictly unnecessary.
 

OldMathsGuy

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Most unfortunate and can be unfair. With dy/dx in factored form we should only need to investigate the signs of the factors without actually evaluating it, as that can be time-consuming and strictly unnecessary.
My understanding is that as long as there is evidence that the positive or negative nature of an expression has been considered by the candidate (such as the factorized expressions you mention to the side of the grid: +ve x -ve x -ve = +ve), then the mark will be awarded. However if there is no evidence that this has been considered, and the marking structure is such that this is one of the aspects required for full marks then the student is going to be missing a mark. The important thing for students here is to always give some form of reasonable evidence that the positive or negative nature has been considered and not to be complacent. I might have to check this up again, but that's my current understanding.

Best Regards
OldMathsGuy
 

Alkanes

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Oh and when testing for inflexion points make sure you but like some statement under your table. For instance, since there is a change in concavity, there is an inflexion point at (x,y).
 

nightweaver066

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Oh and when testing for inflexion points make sure you but like some statement under your table. For instance, since there is a change in concavity, there is an inflexion point at (x,y).
I was also advised to use numerical values for the first derivative table test as well as writing a statement below it explaining how the results in the table show the behaviour of the curve about the point.
 

Annum

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Hey guys I really need help with this question, i hope you can help me because Im getting confused to how its nature is of a minimum turning point.

Q: Find the stationary points and determine its nature:

y= x^4 + 2

Im really getting confused with this maximum and minimum stuff please help me out.
thanks :)
 

SpiralFlex

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Hey guys I really need help with this question, i hope you can help me because Im getting confused to how its nature is of a minimum turning point.

Q: Find the stationary points and determine its nature:

y= x^4 + 2

Im really getting confused with this maximum and minimum stuff please help me out.
thanks :)


































 
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bleakarcher

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y=x^4+2
dy/dx=4x^3
d^2y/dx^2=12x^2
Stationary pts. occur when dy/dx=0,
=>x=0
When x=0,
=>d^2y/dx^2=0
Hence, a horizontal pt. of inflection occurs at (0,2).
 

Carrotsticks

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y=x^4+2
dy/dx=4x^3
d^2y/dx^2=12x^2
Stationary pts. occur when dy/dx=0,
=>x=0
When x=0,
=>d^2y/dx^2=0
Hence, a horizontal pt. of inflection occurs at (0,2).
Just because f'(x) = 0 and f''(x) = 0, it does not necessarily imply a HPOI.
 

SpiralFlex

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What other situations are there?


One example mainly multiple roots in the form

Where n is an integer greater than or equal to 3. Not necessarily a horizontal point of inflexion will occur when both first and second derivative equals to zero.
 

Drongoski

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The graph of y = x^4 + 2 is simply a U-shaped (concave-up) curve with y-intercept of 2. No point of inflexion. In fact such functions are used to show, as Carrot indicated, that f'(0) = 0 and f"(0) = 0 does not imply we have a point of inflexion.
 
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bleakarcher

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The graph of y = x^4 + 2 is simply a U-shaped (concave-up) curve with y-intercept of 2. No point of inflexion. In fact such functions are used to show that, as Carrot indicated, that f'(0) = 0 and f"(0) = 0 does not imply we have a point of inflexion.
True, how come its not a minimum then?

EDIT: i screwed up guys sorry lol. i learnt something from spiral.
 
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