Mathematical Methods CAS Exam 2 Discussion - How was it??

[Water]

Just one question, why can m = 0, for stationary points. Doesn't cubics have stationary point of inflections.? Even when its most basic of b^3 (pun)

[BubbleWrapMan]

Just one question, why can m = 0, for stationary points. Doesn't cubics have stationary point of inflections.?

Not always.

[gossamer]

Just one question, why can m = 0, for stationary points. Doesn't cubics have stationary point of inflections.? Even when its most basic of b^3 (pun)

Water, I'm fairly sure a stationary point is defined as where f'(x)=0

[Panicmode]

Just one question, why can m = 0, for stationary points. Doesn't cubics have stationary point of inflections.?

Remember the question before how you showed the derivetave is greater than or equal to five (hence doesn't equal 0 for no stationary points?)

There is such a thing as non-stationary point of inflection.

[kenny_]

For the mean question, are you sure upper bound is infinity? Cause if you use infinity it doesn't add up to 1 and therefore it isn't a pdf? I made the upper bound = b and solved for b. which was 6.something then used that to find the mean. E(x) = 3.2365...

[b^3]

Just one question, why can m = 0, for stationary points. Doesn't cubics have stationary point of inflections.? Even when its most basic of b^3 (pun)

I actually got this wrong and forgot the 0 in the second part of the question. But not all cubics have stationary points ->http://www.wolframalpha.com/input/?i=x%5E3%2Bx%5E2%2Bx%2B1
e.g. y=x^3+x^2+x+1 doesn't have one.

[BoredSatan]

For the mean question, are you sure upper bound is infinity? Cause if you use infinity it doesn't add up to 1 and therefore it isn't a pdf? I made the upper bound = b and solved for b. which was 6.something then used that to find the mean. E(x) = 3.2365...

no it only works if its inifinity.

i tried on my cas and its definately equal to 1

[thatisanote]

Just one question, why can m = 0, for stationary points. Doesn't cubics have stationary point of inflections.?

Remember the question before how you showed the derivetave is greater than or equal to five (hence doesn't equal 0 for no stationary points?)

There is such a thing as non-stationary point of inflection.

Yes there is sorry! And in fact I read this in some old vcaa thing or the DHA book last night.
There is definitely a regular POI, where the dy/dx doesn't go to zero.

[BubbleWrapMan]

For the mean question, are you sure upper bound is infinity? Cause if you use infinity it doesn't add up to 1 and therefore it isn't a pdf? I made the upper bound = b and solved for b. which was 6.something then used that to find the mean. E(x) = 3.2365...

It was equal to 1 though.

[kenny_]

For the mean question, are you sure upper bound is infinity? Cause if you use infinity it doesn't add up to 1 and therefore it isn't a pdf? I made the upper bound = b and solved for b. which was 6.something then used that to find the mean. E(x) = 3.2365...

no it only works if its inifinity.

i tried on my cas and its definately equal to 1

What about in later questions when they tell you that Pr(y<3) = 9/26.
If you do Pr(Y>3) using calc then its Int 3 to 4 y/16 + int 4 to infinity e^-.25(y-4) and i get 1.218?

EDIT: ok wtf i just deleted it all and entered it again and got 0.71... FUCKKK

[Anon123]

aww man, so depressing getting the first question of ER wrong >.>

Why would vcaa ask an apparently "spesh" question...thats so rat for non spesh students

edit: how many marks for doing
V = 6075 - t^2/5
0 = 6075 - t^2/5
t=45/sqr15 minutes

1?

[duquesne9995]

aww man, so depressing getting the first question of ER wrong >.>

Why would vcaa ask an apparently "spesh" question...thats so rat for non spesh students

same here >_>

[Panicmode]

aww man, so depressing getting the first question of ER wrong >.>

Why would vcaa ask an apparently "spesh" question...thats so rat for non spesh students

same here >_>

It wasn't a spesh question, just spesh kids would've found it easier because it's similar to the easier problems they encounter.

[thushan]

Did the last question of the Methods exam, it was challenging, especially the last part of the last question, where I had a dodgy explanation...

[Anon123]

Did the last question of the Methods exam, it was challenging, especially the last part of the last question, where I had a dodgy explanation...

Yeah I actually had no idea what the hell they were on about, I did not understand the question at all....what the hell was k? I still managed to get all of it right bar the very last question, but my understanding of what was going on...was 0