Mathematics Question Thread

[RuiAce]

Ah, now I see the confusion. I'll fix that up.

[winstondarmawan]

For this question (2012 HSC):
https://scontent-syd2-1.xx.fbcdn.net/v/t35.0-12/22450384_1859562304360226_1131010543_o.jpg?oh=c9539facf7d280f9852385e9ac2652e1&oe=59E0BC01
BOS solutions: https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/22414623_1348343865291133_172365985_n.png?oh=4e05da4594845a032459785e2fe7ee0a&oe=59E12EB3
I'm not sure why they let discriminant = 0 when there are two solutions. Also an explanation for the solution to (ii) would be appreciated.
TIA

[RuiAce]

For this question (2012 HSC):
https://scontent-syd2-1.xx.fbcdn.net/v/t35.0-12/22450384_1859562304360226_1131010543_o.jpg?oh=c9539facf7d280f9852385e9ac2652e1&oe=59E0BC01
BOS solutions: https://scontent-syd2-1.xx.fbcdn.net/v/t34.0-12/22414623_1348343865291133_172365985_n.png?oh=4e05da4594845a032459785e2fe7ee0a&oe=59E12EB3
I'm not sure why they let discriminant = 0 when there are two solutions. Also an explanation for the solution to (ii) would be appreciated.
TIA

Two solutions for x, yes, but only one solution for y. Focus on the y-coordinate of the points of intersection, not the x-coordinates.
__________________________________________

I will do things a bit differently. I'm not fully sure how they were able to assume stuff so easily.

[itssona]

heya pls help with how to do this
find the equation of the parabola passing through (-2,1) with vertex (0,0) and axis x=0

[RuiAce]

heya pls help with how to do this
find the equation of the parabola passing through (-2,1) with vertex (0,0) and axis x=0

[itssona]

thank you^
also
does the line 3x + 4y=5 represent a focal chord o n the parabola x^2=5y

whats the best method? just subbing im?  or could i equate gradients..

[RuiAce]

thank you^
also
does the line 3x + 4y=5 represent a focal chord o n the parabola x^2=5y

whats the best method? just subbing im?  or could i equate gradients..

A focal chord passes through (0,a). In your case, a=5/4 so you just need to check if the point (0,5/4) lies on the line.

[hobocop]

Hey, so when answering graph questions, would you draw it out in pencil first then when finalised you would go over it in pen?

Would this be a good idea, in regards for our answer being able to be scanned. I'm just afraid it would be too time consuming.

[bdobrin]

Hi,

I was just wondering if someone could tell me for a distance travelled question how I do this.

| 2-4ln2 | (there are absolute values on the outside)

Do i just treat it as normal and make it -(2-4ln2) and +(2-4ln2)?

Thanks,
Ben

[RuiAce]

Hey, so when answering graph questions, would you draw it out in pencil first then when finalised you would go over it in pen?

Would this be a good idea, in regards for our answer being able to be scanned. I'm just afraid it would be too time consuming.

By the time I was in Year 12, I just drew all of my graphs in pen on the go, and I had no problems with doing so.

If you want to use this approach, it's viable only if it won't eat into valuable time for other questions at all. You should draw your x and y axes in pen immediately, and then draw it in pencil as fast as you can. Then, don't come back to it until you have time to, and that's when you go over it in pen.

[RuiAce]

Hi,

I was just wondering if someone could tell me for a distance travelled question how I do this.

| 2-4ln2 | (there are absolute values on the outside)

Do i just treat it as normal and make it -(2-4ln2) and +(2-4ln2)?

Thanks,
Ben

[hobocop]

By the time I was in Year 12, I just drew all of my graphs in pen on the go, and I had no problems with doing so.

If you want to use this approach, it's viable only if it won't eat into valuable time for other questions at all. You should draw your x and y axes in pen immediately, and then draw it in pencil as fast as you can. Then, don't come back to it until you have time to, and that's when you go over it in pen.

Thanks for your answer.

But would it be detrimental for me if I leave it in pencil? I use 2B lead.

[RuiAce]

I can't imagine it being overly detrimental, but I would very strongly advise against it. When I bought all my exam responses back from 2015, I saw how terrible the scan quality was. It made me question if a 4B+ (if not 6B) pencil was required for the scan to pick it up.

[mitchello]

Heyo, could I please have help with this question:
'Helen has just retired with $500000 in her account and wishes to start an annuity. She intends to withdraw $M at the end of each year for 30 years. Reducible interest is calculated at 6% p.a., compounded annually just before each withdrawal.

Calculate $M, the amount of each withdrawal.' (3 marks)

[Natasha.97]

Heyo, could I please have help with this question:
'Helen has just retired with $500000 in her account and wishes to start an annuity. She intends to withdraw $M at the end of each year for 30 years. Reducible interest is calculated at 6% p.a., compounded annually just before each withdrawal.

Calculate $M, the amount of each withdrawal.' (3 marks)

Hi!
Financial maths is not my strongest topic so I'm not 100% sure if this is correct:



Hope this helps