Fake HSC paper (1 Viewer)

[lolokay]

ii)
dI/dx > 0 if P<0
both bracketed terms of P are > 0. First one obviously is since all terms>0
for the second bracket
x² + 64 + 225 - 16.sqrt[289] > 0
x² + 17*17 - 16*17 > 0
x² + 17 > 0
is true therefore it is always greater than 0
so P<0 for 2x<0 and P>0 for 2x>0

so brightness is increasing for x<0, decreasing for x>0

iii)
P = 2x(x²+ 260)(x²-60)
this is >0 for x>sqrt.60 or -sqrt.260<x<0
decreasing for x<-sqrt.260 or 0<x<sqrt.60
and stationary at x = 0, sqrt60, -sqrt260

 

[Darrow]

ii)
dI/dx > 0 if P<0
both bracketed terms of P are > 0. First one obviously is since all terms>0
for the second bracket
x² + 64 + 225 - 16.sqrt[289] > 0
x² + 17*17 - 16*17 > 0
x² + 17 > 0
is true therefore it is always greater than 0
so P<0 for 2x<0 and P>0 for 2x>0

so brightness is increasing for x<0, decreasing for x>0

iii)
P = 2x(x²+ 260)(x²-60)

this is >0 for x>sqrt.60 or -sqrt.260<X<0< p>
decreasing for x<-sqrt.260 or 0<X<SQRT.60< p> and stationary at x = 0, sqrt60, -sqrt260

Its times and working out like this, which make you question: Is it worth it for those 2 or 3 marks?

 

[tau281290]

This question is from the 2U 2002 HSC paper Q10.

i) is actually pretty easy, took me 3 lines.

ii) and iii) are a bit harder, but still only 2 marks each. So if you say i) is ridiculous, then why didn't you say ii) and iii) even more ridiculous??

 

[lyounamu]

This question is from the 2U 2002 HSC paper Q10.

i) is actually pretty easy, took me 3 lines.

ii) and iii) are a bit harder, but still only 2 marks each. So if you say i) is ridiculous, then why didn't you say ii) and iii) even more ridiculous??

I don't know. May be different people think differently. I actually found part ii) and iii) easy. For part i), I didn't practise many questions on algrebraic manipulation...that's why it took me 10 lines to work that out.

And if it took you 3 lines, why not show us?

 

[tau281290]

This is what I did:

 

[lolokay]

I think you would need more working than that for the differentiation

 

[tau281290]

y

 

[lolokay]

y

it just seems like you're doing to much in the one step for a show question, but I'm not sure how marking works, so maybe it would be acceptable

I suppose if you showed the derivatives of the separate fractions, and then went from there to the 2nd line it would be a bit more clear.. but I dunno, it would depend on how the question is marked.

 

[tau281290]

YOu won't lose a single mark as long as ur not fudging it

 

[lyounamu]

I seriously agree with lolokay. You just squeezed tonnes of stuff every line. If I did that, I could just write two lines, wth.

 

[tau281290]

but that's what i did, i am just trying to show you my way of doing it, as you have requested. you don't have to do it this way.

 

[lolokay]

YOu won't lose a single mark as long as ur not fudging it

you could quite easily fudge that working (just write out the expression for -2P/Q, then multiply each part of P by -2, on the previous line, maybe even simplify that on the line before it..)

 

[tau281290]

Prove it

 

[tommykins]

回复: Re: Fake HSC paper

YOu won't lose a single mark as long as ur not fudging it

Wrong, you will lose a mark.

it just seems like you're doing to much in the one step for a show question, but I'm not sure how marking works, so maybe it would be acceptable

I suppose if you showed the derivatives of the separate fractions, and then went from there to the 2nd line it would be a bit more clear.. but I dunno, it would depend on how the question is marked.

If its a SHOW question, then you MUST show ALL lines of working.

If it was a "deduce", then tau's method is okay, but it's a show so he may (most likely) lose a mark for incomplete working.

 

[tau281290]

you could quite easily fudge that working (just write out the expression for -2P/Q, then multiply each part of P by -2, on the previous line, maybe even simplify that on the line before it..)

Honestly, how can you ever fudge a question to such high precision? Even if it is fudged (but it is not), you wouldn't even get the -1 and for that particular part.

 

[tau281290]

Re: 回复: Re: Fake HSC paper

Wrong, you will lose a mark.


If its a SHOW question, then you MUST show ALL lines of working.

If it was a "deduce", then tau's method is okay, but it's a show so he may (most likely) lose a mark for incomplete working.

Good reasoning, that's why I won't do that in the exams :wave:

 

[lolokay]

Honestly, how can you ever fudge a question to such high precision? Even if it is fudged (but it is not), you wouldn't even get the -1 and for that particular part.

I don't really see how what I described requires high precision; it's just expanding -2P/Q a bit.

 

[tau281290]

I never said you description requires high precision. I am saying my workings are in high precision =).

 

[lolokay]

I never said you description requires high precision. I am saying my workings are in high precision =).

..how? one line of working is just the terms for -2P/Q; the one before it just has each term in the brackets multiplied by -2 (except one has it written as -1(2 )

ehh nevermind..

 

[dood09]

are you fucking retarded??

its easy