Carrotsticks' Solutions 2015 Extension 2 HSC (1 Viewer)

m_wahwah

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I think you have Question 2 wrong? It should be a, B gives you 7+24i
 

Ekman

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For Question 2 of MC I got A not B. Reason being is because when you say (x+iy)^2 = 7-24i, x^2-y^2 = 7 and 2xy = -24. So both x and y cant be negative at the same time otherwise you cant get -24. Hence B is wrong.
 

Simplyy

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umm, MCQ 2.A? Isn't it? B) doesn't work cause, for example, if you sub it in, (-4-3i)^2 = 16-9+24i = 7+24i not 7-24i.
Or if you prefer the longer method, of equating real and imaginary components/completing the square, x^2-y^2 = 7, 2ixy = -24, xy = -12, by inspection, x=4, y=-3 or x=-4, y=3. Therefore, z = 4-3i (A) or -4+3i...

Edit: Jokes. already posted.
 

leehuan

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12 a) (iii)

I think it was z^2 - conjug(z)
Not conjug(z^2)
 

Carrotsticks

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Fixed the errors!

Funnily enough, those were pretty much the exact same errors I made when I did my Extension 2 HSC.
 

lekawaiicupcake

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Hey man thanks for doing this :)
One thing though, question 12 a) iii) asks for z^2-z(conjugate), not z^2-(z(conjugate))^2

(Also sorry for the formatting.)

Edit: Looks like someone else beat me to spotting it ^^
 

tywebb

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Thanks Carrotsticks :) Can you also please up the paper :)
He doesn't need to.

beanbean already did:

http://community.boredofstudies.org/1160/mathematics-extension-2/344061/maths-extension-2-thoughts-6.html#post7054013

Also there also a better quality one from WhoStanLeee in this post: http://community.boredofstudies.org/1160/mathematics-extension-2/344061/maths-extension-2-thoughts-8.html#post7054201

It's better quality but unfortunately is missing some bits (Q11 and 15 b and c - see below in post #24 in this thread for those which I extracted from beanbean's version).
 
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Simplyy

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umm, for 11. b) ii) argz = pi - arg(1/sqrt3) = pi - pi/6 = 5pi/6 not 2pi/3
 

Carrotsticks

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Have updated the link! Cheers for pointing out those errors. Silliest of things.
 

InteGrand

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