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

[Anon123]

Wait what was the answer for 1.a)
i thought it was simply:
t^2/5=6075
t^2/5-6075=0
t=45root(15)
=174.28 minutes
=175

so did i...apparently its some "spesh" (or not) differential equations thing...idk, the answer is 45 though

[Donkey22]

I fkn wrote 'dx' not 'dy'

Do i still get marks for correct answer..?

[tigerfan11]

Wait what was the answer for 1.a)
i thought it was simply:
t^2/5=6075
t^2/5-6075=0
t=45root(15)
=174.28 minutes
=175

so did i...apparently its some "spesh" (or not) differential equations thing...idk, the answer is 45 though

okay so that will be 0/3 ?

[luffy]

@Luffy -> because x = 0 is the only stationary point along the interval (it's a local maximum though) when k is higher than 5root(37)/74; the function would be decreasing over that interval with no other stationary point in that interval.

Ohh right fair enough. Thanks a lot for clearing that up. I doubt VCAA would look for an answer like that though. Nonetheless, it definitely is the best one that a student could give.

I found that question really interesting though. Never come across something quite like it and the question had me thinking even after doing the exam.

[BubbleWrapMan]

I fkn wrote 'dx' not 'dy'

Do i still get marks for correct answer..?

You'll probably get 2 marks out of 3.

[b^3]

I fkn wrote 'dx' not 'dy'

Do i still get marks for correct answer..?

You'll probably get 2 marks out of 3.

I wrote dx as well, realised my mistake as soon as I finished the x, rubbed it out and then wrote down dx again! I thought to myself "wtf are you doing", rubbed it out again and put dy. We do stupid things under exam conditions.

[luken93]

What does everyone think about 3dii, do you reckon they'll pay it for being unclear?

(You weren't meant to use your value found from part i fml)

[cltf]

I fkn wrote 'dx' not 'dy'

Do i still get marks for correct answer..?

You'll probably get 2 marks out of 3.

I wrote dx as well, realised my mistake as soon as I finished the x, rubbed it out and then wrote down dx again! I thought to myself "wtf are you doing", rubbed it out again and put dy. We do stupid things under exam conditions.

You would lose that mark once over the entire exam, so it you happen to do it again in other questions, you'll only lose the one mark overall.

[thatisanote]

What does everyone think about 3dii, do you reckon they'll pay it for being unclear?

(You weren't meant to use your value found from part i fml)

That's insanely dodgy, considering it says 'if *THIS* stationary point occurs...' as if referring to di

So hopefully. I'm not sure if I did or did not.

[Random_Guy]

I don't understand why people used differential equations for Question 1a. The questions says that the oil "will leak into the sea at a rate of (t^2)/5 litres per minute." Therefore, the volume is decreasing by (t^2)/5 per minute. I interpreted this as being 6075 - (t^2)/5, and this seems very logical.

If the question reads "The volume of oil is changing/decreasing at a rate of (t^2)/5 per minute", then dV/dT = (t^2)/5 would make sense.

[b^3]

What does everyone think about 3dii, do you reckon they'll pay it for being unclear?

(You weren't meant to use your value found from part i fml)

What do you mean you weren't meant to use the value? It says "If this stationary point occurs at a ....."

[andrew.michail]

Tasmania Jones was eaten by a crocodile while swimming up the river to the desalination plant.. R.I.P Tasmania

[Panicmode]

What does everyone think about 3dii, do you reckon they'll pay it for being unclear?

(You weren't meant to use your value found from part i fml)

Lol, what do you mean? It said find the value of c if there is only one stationary point (this value of c is that same for all values of k if there is only one stationary point), it then goes on to say that if this stationary point (not points) occurs at this point blablabla...

What do you mean the value from before wasn't meant to be used. It's the same equation with only one stationary point. I's confused

[Hamdog17]

What does everyone think about 3dii, do you reckon they'll pay it for being unclear?

(You weren't meant to use your value found from part i fml)

Yeah should, it'll be very unfair if they don't. I also used my answer from 3di

[BubbleWrapMan]

I'm sure you use the answer from 3di

You solve g'(x) = 0 when c = 4/3 to get x = -2/3

Then solve g(-2/3) = -2/3 for k to get k = -10/27