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Carrotsticks' 2017 Mathematics Extension 2 solutions (1 Viewer)

Carrotsticks

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Hey Carrotsticks, you reckon I would lose 1/2 marks if I got a = 1 and 1/3, but I didn't have the plus minus?
I don't even think you would lose any marks. Unless I am mistaken, even in the course it's not clear if A must be zero or not. If NESA can't decide then surely they won't dock you down for that.
 

Carrotsticks

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Weird, I fixed the locus diagram and then it stuffed up again.
 

raz999

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Is the answer to the conics one a=+-1, +-1/3?
I thought by definition, a>0
 

Raeservoir

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That was impressively quick! Gonna ask my own question with a careless blunder (technically 2) I made: ellipse/hyperbola 15c.

- part i: pretty sure I did c^2 - a^2 instead of a^c - c^2 - my bad for not checking the proof in the question

- part ii: swapped + and - for hyperbola and ellipse eccentricities, so I did a^2 - b^2 and c^2 + d^2, which countered the mistake I made in part i allowing me to prove it.

Are these two mistakes worth -1 each? If so, unfortunate... they are technically 2 separate errors.
 

SaltSolutionPromo

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Most of my cohort thought it was easy actually (my cohort is around 119 students). Essentially everyone I know who knows what they're doing thinks they got 90+ raw, and most of the top students (by top I mean top 40 lol) have lost maximum 5 marks so far.
 

pikachu975

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Most of my cohort thought it was easy actually (my cohort is around 119 students). Essentially everyone I know who knows what they're doing thinks they got 90+ raw, and most of the top students (by top I mean top 40 lol) have lost maximum 5 marks so far.
Woah do you go like james ruse?
 

Carrotsticks

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Okay I'm going to address the a=plus/minus versus a>0 issue.

We say a>0 to keep things simple. That is, so that we may assign a physical thing (length of semimajor axis) to the value of "a". But mathematically, this is not a restriction.

Q: Will I get penalised for not doing A=plus/minus ?

A: I don't think so. I reckon you'll be safe leaving it at 1/3 and 1.
 

Carrotsticks

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That was impressively quick! Gonna ask my own question with a careless blunder (technically 2) I made: ellipse/hyperbola 15c.

- part i: pretty sure I did c^2 - a^2 instead of a^c - c^2 - my bad for not checking the proof in the question

- part ii: swapped + and - for hyperbola and ellipse eccentricities, so I did a^2 - b^2 and c^2 + d^2, which countered the mistake I made in part i allowing me to prove it.

Are these two mistakes worth -1 each? If so, unfortunate... they are technically 2 separate errors.
Nah you'll probably only lose one mark overall.
 

SaltSolutionPromo

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But even in most years, we only get like 70-80 E4 out of 120 circa. Unless our cohort this year is stronger, which maybe the case since we had a 100% B6 rate on 2U accelerated last year.
 

jjHasm

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oops i thought i was getting 68-70, looking at solutions probably getting 60ish, what do you guys reckon this would moderate to? 85+?
 

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