Post Your Problem Here (1 Viewer)

[victorling]

hello, everyone!!

i have just done my hsc and i got 96% for both maths3 and 4u

My intention to post my score is to encourage you people to post ur problem here , so to make u know that i may be of some possible help to your questions

Come on!

 

[abdooooo!!!]

i see you have taken my advise victor... now enlighten us.

 

[sylvia87]

hey ! i am doing extension maths.. but i am just doing alrgiht! and i mean JUST! but like i want to keep it becoz i dont want to have exactly 10 units u noe!

but as i said i am not doing as good! as other ppl!
will it affect my 2unit maths mark becoz i did extension?.. when in the uai it will count all my other subjects.

 

[victorling]

Originally posted by sylvia87
hey ! i am doing extension maths.. but i am just doing alrgiht! and i mean JUST! but like i want to keep it becoz i dont want to have exactly 10 units u noe!

but as i said i am not doing as good! as other ppl!
will it affect my 2unit maths mark becoz i did extension?.. when in the uai it will count all my other subjects.

umm...yes..it will definitely lower your uai down to a certain extent....
but no worry now, for u still have time!!

 

[victorling]

Originally posted by GuardiaN
hey, never mind Victor. It's pretty easy, its just that I don't do physics and I didn't know anything about LR circuits (whatever the hell THEY are).

sorry, i dont know what exactly your question is...i have looked at your question posted previousl but i still don't understand

 

[Grey Council]

ah, don't worry about it. Its just a bullshit Growth and Decay question thats worded REALLY stupidly. Like VERY stupidly. It requires all this bullshit physics knowledge, which is why im pissed off. I spent like an hour on that question, and then someone tells me I had to know physics. berloody...

btw, sylvia, your extension maths mark has no affect on your 2 unit maths mark. You can fail 3u, and it won't make a difference to your 2 u maths mark. But if you put a little effort in, you can go really well in maths.

 

[overwhelming]

Okay victorling - help us with the following:

Show that x^2/x^4+x^2+1 is less than or equal to 1/3, for all real x.

 

[xiao1985]

Originally posted by overwhelming
Okay victorling - help us with the following:

Show that x^2/x^4+x^2+1 is less than or equal to 1/3, for all real x.

uhm some ambiguity here... is it :

(x^2/x^4) + (x^2) + 1 or
x^2/[(x^4) + (x^2) + 1] or something else??

 

[Rahul]

the latter...i think

 

[Grey Council]

try to prove true, or otherwise, for both.

 

[evilc]

Originally posted by overwhelming

Show that x^2/x^4+x^2+1 is less than or equal to 1/3, for all real x.

working might be a bit dodgy, but oh well

 

[Grey Council]

isn't the whole point of this thread to let victorling answer questions? Let him, he wants to help out.

btw, victorling, i've posted 4 questions I couldn't do in the extension 2 forums. its complex numbers.

 

[kimmeh]

:rofl: he's posted about his tutoring everywhere... so for now, i guess he's run away scared because of the question u asked he's not what he seems to be people! ahahaa lets link this to his offering tuition thread muahaha no customers

 

[KeypadSDM]

Originally posted by evilc
working might be a bit dodgy, but oh well

Yeah, it is a bit dodgy. You have to prove the inequality, you can't assume it, plus you didn't answer the question.

Alternative: (Note, no use of f"(x), which would probably be quicker)

RTP: x^2/(x^4 + x^2 + 1) <= 1/3

Let f(x) = x^2/(x^4 + x^2 + 1)

f'(x) = 2x(1 - x^2)/(x^4 + x^2 + 1)^2 (Trust me)

For f'(x) = 0, x = -1, 0, +1

Now for the annoying bit, where I should have done an f"(x) check.

Let, #x = (delta)x

f'(-1 - #x) > 0
f'(-1 + #x) < 0
f'(-#x) < 0
f'(#x) > 0
f'(1 - #x) > 0
f'(1 + #x) < 0

Hence maxima at x = 1, -1 and minima at x = 0

(Note, f(x) = f(-x))

f(+/-1) = 1/3

:. f(x) <= 1/3
x^2/(x^4 + x^2 + 1) <= 1/3

Q.E.D.

 

[~*HSC 4 life*~]

umm what particular topic does that q fall under?

 

[~*HSC 4 life*~]

never mind...its inequalities so i suppose it'd be under 'equations'

 

[evilc]

yeah, i was going to sketch the function and prove it that way, but couldn't be bothered to

 

[pc_wizz]

Find an expression for y in terms of x:


log y = (log b) + cx

all the above are base 10


PCWIZZ

 

[victorling]

Originally posted by pc_wizz
Find an expression for y in terms of x:


log y = (log b) + cx

all the above are base 10


PCWIZZ

SOLUTION: log y - log b = cx

log(y/b) = cx

therefore, 10^cx = y/b

y = b*(10^cx)

= b(10^cx)

 

[victorling]

sorry for not answering the previous questions posted
i was too busy doing my voluntary work....*_*
got to reduce the workload....