VCAA 2006 QS. 4B) iii

[PringlePop]

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!

[superflya]

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.

[PringlePop]

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

[wildareal]

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!

[wildareal]

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

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

[taiga]

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

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

[mikee65]

would you guys automatically think to times f(x) by 4?

[jto1292]

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 :/