# General thoughts- Extension 1 maths (1 Viewer)

#### nathank111

##### hu?
t'was better than i expected. Although i only completed 77%....
Apathy got the better of me and i didn't study a whole lot... time to make up for it in Ancient i guess...

good luck to the rest of you

#### Legham

##### Active Member
Also for 1c) what was the answer? I'm not sure if I got that one
Im not sure about that one either. i just had 3x^2/(1 + (x^4)^2) i think. I was tossing up between putting the 3x^2 in or not, cause i didnt know if we had to do the differential of inside the brackets :S (x^4) like in the chain rule..

#### woho

##### Member
Legham said:
Im not sure about that one either. i just had 3x^2/(1 + (x^4)^2) i think. I was tossing up between putting the 3x^2 in or not, cause i didnt know if we had to do the differential of inside the brackets :S (x^4) like in the chain rule..
Yeh that's what i got too

Hope its right!

EDIT: actually i got the eqn below. sorry, didnt read ur post properly

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#### lilfrenchi

##### New Member
Legham said:
Im not sure about that one either. i just had 3x^2/(1 + (x^4)^2) i think. I was tossing up between putting the 3x^2 in or not, cause i didnt know if we had to do the differential of inside the brackets :S (x^4) like in the chain rule..
for that 1 i just let u=x^4
du/dx = 4x^3
d(tan^-1 u)/du = 1/1+u^2
du/dx * d(tan^-1 x^4)/du = 4x^3/1+(x^4)^2

#### joshuajspence

##### Member
lilfrenchi said:
i counted the 4 children as one since they are seatin together then multiplied it by the way they can be arranged together. then divided that by 6!
therefore 3!*4!/6!
duno if im right tho
This is how I did it...

P1 = parent 1
P2 = parent 2

_ = kids

P1 P2 _ _ _ _ = 4!

P2 P1 _ _ _ _ = 4!

_ _ _ _ P1 P2 = 4!

_ _ _ _ P2 P1 = 4!

therefore total ways = 4 * 4!

total = 6!

therefore 4* 4! / 6!

G

#### gaoOO

##### Guest

P1 _ _ _ _ P2
P2 _ _ _ _ P1

?

yeah, i'm pretty confident about 1/5

#### lilfrenchi

##### New Member
joshuajspence said:
This is how I did it...

P1 = parent 1
P2 = parent 2

_ = kids

P1 P2 _ _ _ _ = 4!

P2 P1 _ _ _ _ = 4!

_ _ _ _ P1 P2 = 4!

_ _ _ _ P2 P1 = 4!

therefore total ways = 4 * 4!

total = 6!

therefore 4* 4! / 6!
u forgot P1 _ _ _ _ P2 = 4!
and P2 _ _ _ _ P1 = 4!
which gives 6*4!/6!
which is the same as 3!*4!/6!

#### joshuajspence

##### Member
woho said:
What about P1 _ _ _ _ P2?
damn i thought the parents had to sit together

#### fishy89sg

##### Member
lilfrenchi said:
for that 1 i just let u=x^4
du/dx = 4x^3
d(tan^-1 u)/du = 1/1+u^2
du/dx * d(tan^-1 x^4)/du = 4x^3/1+(x^4)^2
isnt that supposed to be 8 since

d(tan^-1 u)/du = 1/1+u^2
= 1/1+x^8 since u^2 = x^8

G

#### gaoOO

##### Guest
fishy89sg said:
isnt that supposed to be 8 since

d(tan^-1 u)/du = 1/1+u^2
= 1/1+x^8 since u^2 = x^8
nah, what she has is (x^4)^2 = x^8

it's the same thing

#### sting24

joshuajspence said:
This is how I did it...

P1 = parent 1
P2 = parent 2

_ = kids

P1 P2 _ _ _ _ = 4!

P2 P1 _ _ _ _ = 4!

_ _ _ _ P1 P2 = 4!

_ _ _ _ P2 P1 = 4!

therefore total ways = 4 * 4!

total = 6!

therefore 4* 4! / 6!
u forgot that the parents dont have to sit next to each other

#### fishy89sg

##### Member
gaoOO said:
nah, what she has is (x^4)^2 = x^8

it's the same thing
LMAO OMG IM BLIND.... feel like deleting my post(s)

overalll, i thought it was a good exam

#### forevaunited

##### Member
Well i got that tan one right . . . not much else though. Ran out of time so i rushed question 5. I think i will probably get about 3/4 outta 12 for question 5. First part i misread - thinking it said the straight line not the arc. So i kept trying to use alternate angle from tangent property - needless to say, it didn't work.

i got 3!/6! for the probability and forgot the 4!. The simultaneous equations i skipped because i was desperately falling behind with time. Same with parametrics, although i dont think i would have got that if i had more time anyway.

So yeah im pretty sure i did fairly bad, max i think ill get is about 65/84

#### cc =)

##### New Member
mrzeidan1 said:
That exam was alright i thought

i got 283 for the parachuting lady

and 4!x3!/6! for the probability

missed a few marks, 1ST PARAMETRICS WHAT THE HELL , and also 6b.iii and 7aii.

finished the projectile hopefully its right

hoping for a 75+/84
it was easier than last year`s

i left out those same questions =(

did anyone do 6 b ii ?

there wasnt any binomials this yr and i studied for it =( BUT thats a GOOD thing cos binomials sucks lols

#### Originality

##### Member
Wow...that was actually easier than i expected it to be...i think it is probably my least hated exam so far...which is nice. I actually kinda enjoyed doing it.
I was so glad that they didn't have on of those really hard binomial questions. I just can't seem to get my head around them.
And i wasn't wishing for more time, because i git do do each question to the best of my ability...and i answered alot more questions than i anticipated i would.
And my theory worked (better than expected too)...i decided that if i went into the exam with no confidence whatsoever...then when i saw the paper...and realised how bloody hard it was...i would have no confidence to be shattered, and hence i couldn't freak out and screw up...the great thing was that when i say that the paper was easier than i expected...i got confidence!!! YAY!!!
Overall...i am very pleased with the exam, and i think that i will get a good mark...and a much better one than i anticipated during the exam.

I hope everyone else found the paper ok, and good luck with your last few exams all
I agree with wat u said except that i wanted more time. Was attempting last part of question 7 but i got a lil restless. Did 1st bit though.

I was so glad no binomials. I was think i'd definetly stuff up the binomials.
B4 the test i knew, it wasnt as hard as last yr's. Wen i attempted it, didnt do dat well. So i knew that was the hardest it would get.
But still i got some i couldnt do. But pretty satisfied with the topics in it.

Crap i realised i got the probability wrong, instead of calculating probability, i did "how many ways" can they sit together. -___-

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#### Legham

##### Active Member
lilfrenchi said:
for that 1 i just let u=x^4
du/dx = 4x^3
d(tan^-1 u)/du = 1/1+u^2
du/dx * d(tan^-1 x^4)/du = 4x^3/1+(x^4)^2
I was gonna do that but it specified with respect to x so i didnt think i was allowed to use a substitution but oh well, the answer came out the same i think.

@ nathank111: Yeah, i meant the one that she said.. i read it as x^3 instead of x^4 when i was typing it up just then ^___^

#### Starcraftmazter

##### Member
O...shit, I think I might have forgotten to square x^4 on the tan question
><

Damnit, im so stupid ><

#### hunter1

##### Evolution is a mystery
gaoOO said:
Hope i didn't make any stupid mistakes

i had to fudge the ln (x + root x^2+4 /2) queestion because i didn't know why it was the positive case.

i thought it was a pretty difficult extension 1 test, seemed longer than the past hsc, maybe on par with last year's paper? but i'm not sure. The extension 1 students probably have a better idea of the difficulty than the extension 2 students.

ok, maybe not on par with last year's paper going by what dispryde just said.
I found the exam alright, i just said it was the positive case as ln of a negative number doesn't exist

#### mattmaug

##### New Member
i reckon that was probably the easiest 3 unit paper ive done. even got question 7 which i havent done before