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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: PringlePop on November 06, 2010, 11:52:22 pm

Title: VCAA 2006 QS. 4B) iii
Post by: PringlePop on November 06, 2010, 11:52:22 pm
Why won't my calculator solve for a(or x) in terms of p?

And this question is A LOT of work for just one mark!
Title: Re: VCAA 2006 QS. 4B) iii
Post by: superflya on November 07, 2010, 12:00:55 am
u dont need a calc for that question..

f(1) so sub in x=1, u've got q in terms of p from the previous question so sub that in. the calc can clean up the rest or it can be done by hand.
Title: Re: VCAA 2006 QS. 4B) iii
Post by: PringlePop on November 07, 2010, 12:04:12 am
Soz - I'm looking at the Checkpoints and there is sooo much working out. The guy/girl used a calculator, and I didn't get anything resembling their answer...

Question answered :D

Title: Re: VCAA 2006 QS. 4B) iii
Post by: wildareal on November 07, 2010, 12:04:56 am
This is a question you must do by hand.

It is an incredible amount of working for 1 mark.

f'(x)=3px^2+2qx+4.25=0
4f'(x)=12px^2+8qx+17=0

FACTORISE:

12px^2-12px +17 -17x

12px(x-1)-17(x-1)

therefore:

(12px-17)(x-1)=0

therfore:

x=17/12p or x=1

I cannot believe all that was one mark!

Title: Re: VCAA 2006 QS. 4B) iii
Post by: wildareal on November 07, 2010, 12:05:30 am
Soz - I'm looking at the Checkpoints and there is sooo much working out. The guy/girl used a calculator, and I didn't get anything resembling their answer...

Question answered :D



LOL beat me to it.
I hope I'm right, haven't checked solutions.
Title: Re: VCAA 2006 QS. 4B) iii
Post by: taiga on November 07, 2010, 12:07:50 am
Soz - I'm looking at the Checkpoints and there is sooo much working out. The guy/girl used a calculator, and I didn't get anything resembling their answer...

Question answered :D



LOL beat me to it.
I hope I'm right, haven't checked solutions.

Yeah that's what i got.

your cas wont do that, i tried it with the cas at first
Title: Re: VCAA 2006 QS. 4B) iii
Post by: mikee65 on November 07, 2010, 09:58:19 am
would you guys automatically think to times f(x) by 4?
Title: Re: VCAA 2006 QS. 4B) iii
Post by: jto1292 on November 07, 2010, 10:01:53 am
Cas did it for me :) But instead of 17/12p , it gives 1.41667/p which is the approximation. I had to do further work to get that it was 17/12p :/