# Maths Ext 2 Predictions/Thoughts (1 Viewer)

#### Siwel

##### Active Member
unwatchable. this kid shouldn't even be doing maths let alone 4u. jk jk but thats such a simple mistake how can you screw that up thats worse than my mistake.
yeah i would say messing up algebra is underappreciated marks wise so maybe i get 5, i did have the intent to get the right answer

#### notme123

##### Well-Known Member
yeah i would say messing up algebra is underappreciated marks wise so maybe i get 5, i did have the intent to get the right answer
exactly, might as well give me a sr at this point.

#### Siwel

##### Active Member
exactly, might as well give me a sr at this point.
ngl for the weird circle and ln function volumes i somehow made up my own way to find the volumes rotated and got the right solution

##### -insert title here-
Matrix solutions: https://www.matrix.edu.au/2021-hsc-maths-ext-2-exam-paper-solutions/

Other sites to keep an eye on are

and

Historically Terry Lee used to be the first with solutions up.

Recently he has been beaten by a few others.

Itute are very slow to put them up - maybe a month or so - some say they take a wiser approach than rushing to be the first.

Itute also seem to be consistently the most complete too - even putting them up for Standard 1 - which is very rare.
Matrix didn't put a dashed line for the straight line segment joining z=0 to z=-π. -1 mark.

#### notme123

##### Well-Known Member
ngl for the weird circle and ln function volumes i somehow made up my own way to find the volumes rotated and got the right solution
i didnt even realise you could do have a cube - a hemisphere i did a full integral hahaha

#### tywebb

##### dangerman
unwatchable. this kid shouldn't even be doing maths let alone 4u. jk jk but thats such a simple mistake how can you screw that up thats worse than my mistake.
My criticism stands.

But I want to downplay it. It's not a great drama.

He went through quite a bit of hefty algebra and I'm glad he was the one doing it, not me.

Overall I think he did a great job.

#### notme123

##### Well-Known Member
My criticism stands.

But I want to downplay it. It's not a great drama.

He went through quite a bit of hefty algebra and I'm glad he was the one doing it, not me.

Overall I think he did a great job.
how does one even get chosen to do this.
1. go to a prestigious school which will pay the smh to do this article
2. become ranked first in x2
3. profit

#### Siwel

##### Active Member
how does one even get chosen to do this.
1. go to a prestigious school which will pay the smh to do this article
2. become ranked first in x2
3. profit
on the facebook 2 days before they asked ppl, are you 1st in your school for x2?

#### notme123

##### Well-Known Member
on the facebook 2 days before they asked ppl, are you 1st in your school for x2?
i did not see this and i refresh facebook every 2 seconds

wait which fb page

#### Siwel

##### Active Member
i did not see this and i refresh facebook every 2 seconds

wait which fb page
the 3u and 4u one

#### Siwel

##### Active Member
whatttt i did not know those existed
they do, but honestly no one uses them

#### 5uckerberg

##### Well-Known Member
ah yes the classic article where boomers question why we still do things like this because it has no value to society. a pattern ive noticed is that top schools always get the opp to do this.
You took the words right out of my mouth.

#### s97127

##### Active Member

For this question, i want to prove 5^n -2^n - 3^n > 0 for n>= 2

(2+3)^n - 2^n - 3^n = 2^(n-1).3 + 2^(n-2).3^2 +....+ 3^(n-1) > 0 (QED)

Is this proof correct?

#### AlphaBetaThetaGamma

##### New Member
View attachment 33882
For this question, i want to prove 5^n -2^n - 3^n > 0 for n>= 2

(2+3)^n - 2^n - 3^n = 2^(n-1).3 + 2^(n-2).3^2 +....+ 3^(n-1) > 0 (QED)

Is this proof correct?
I'm really confused at it. Let me see if latex works.
By first glanace no. wat about < .

#### Trebla

View attachment 33882
For this question, i want to prove 5^n -2^n - 3^n > 0 for n>= 2

(2+3)^n - 2^n - 3^n = 2^(n-1).3 + 2^(n-2).3^2 +....+ 3^(n-1) > 0 (QED)

Is this proof correct?
Almost...except you forgot the binomial coefficients.

Also, generally speaking, proving something is positive to prove it is non-zero doesn’t always work (it works in this case though). You can have expressions that can be positive or negative but is non-zero.

#### Eagle Mum

##### Well-Known Member
Correct I got 100 for x1 but i got nowhere close to a state rank.
I imagine that by scaling extension students up, it’s quite compacted at the top, so amongst the cohort with a scaled mark of 100 would be a range of raw marks, but anyone who achieves a raw mark of 100 deserves to be equal first. Students in different schools who achieve a perfect score in the exam shouldn’t be ranked based on school assessments, since assessments aren’t standardised. Congratulations on your awesome achievement!

#### s97127

##### Active Member
Almost...except you forgot the binomial coefficients.

Also, generally speaking, proving something is positive to prove it is non-zero doesn’t always work (it works in this case though). You can have expressions that can be positive or negative but is non-zero.
Thanks. I forgot about coefficients. Regarding the other comment, it only works if all the terms are either greater/lesser than 0.