Official WJEC C1 Discussion Thread 14/01/2013

Know where I can get my hands on a C1 Summer 12 paper? I've done all the others and want more practice!

I'm not too bothered about the mark scheme, I just want more practice.. Is it on your computer?

Can I PM you my email?

Hi,
Can somebody help me with a C1 question please?

I don't understand what to do with questions such as:

Given that the equation:
x^3 - 6x^2 + 20 = k
has three distinct real roots, find the range of possible values for k.

We have previously worked out that there is a maximum at (0,20) and minimum at (4,-12)
(Answer is -12<k<20 )

Thanks!
Tom

ohh! It's obvious now you've said it :L

Cheers

What about this one:

x^3 - 12x + 11 = k
Has only one real root, find the range of possible values for k.
Max at (-2, 27)
Min (2, -5)

I would've said 27>k>-5, but the m/s wants:
k > 27
k < –5

That's what I though originally, but the m/s shows this (



Unless there's a mistake...

Jan '08, Q10 :/

x^3-12x+11

(2,-5)
(-2,27)

They're right

If there is one real root it has yo be outside those barriers because otherwise it'll cross over loads

But it doesnt cross the x-axis outside of that range?
>Side question, what is a real root on a graph? :P

Sorry, being stupid here :/

A y value greater than 27 cant cross the x axis?
And neither can a y value of less than -5?

Or am I thinking about this the wrong way?