You are Here: Home

# How to do this C3 question? Tweet

Maths and statistics discussion, revision, exam and homework help.

Announcements Posted on
IMPORTANT: You must wait until midnight (morning exams)/4.30AM (afternoon exams) to discuss Edexcel exams and until 1pm/6pm the following day for STEP and IB exams. Please read before posting, including for rules for practical and oral exams. 28-04-2013
1. How to do this C3 question?
1 ) The functions f and g are defined for real values of x by

Where a and b are non-zero constants.

Given that and given further that , for all values of , find the set of possible values of .
Last edited by Fusionary; 13-06-2012 at 15:10.
2. Re: How to do this C3 question?
Please post a detailed worked solution in spoiler, thanks.
3. Re: How to do this C3 question?
Sub in what you're given and write the inequality. Post what you get.
4. Re: How to do this C3 question?
5. Re: How to do this C3 question?
(Original post by Fusionary)
Please post a detailed worked solution in spoiler, thanks.
We aren't supposed to give full solutions until we can see that you have had a good go at it. Post what you have done so far.
6. Re: How to do this C3 question?

Now?
7. Re: How to do this C3 question?
(Original post by Fusionary)
You have be told that this is true for all x. I would now put it all on one side to give you a quadratic >0 or <0 then complete the square.
8. Re: How to do this C3 question?

Not sure how to complete the square for this?
Last edited by Fusionary; 13-06-2012 at 15:23.
9. Re: How to do this C3 question?
(Original post by Fusionary)

Not sure how to complete the square for this?
Do you know how to complete the square for one with just numbers in? If so it's exactly the same, just treat the final contant as (b-5) and complete the square as normal.
10. Re: How to do this C3 question?
Good luck for C3!!!
My paper last year in June was lovely, I hope the same for you guys : )
11. Re: How to do this C3 question?
(Original post by Fusionary)

Not sure how to complete the square for this?
Shouldn't the first term be
12. Re: How to do this C3 question?
Hmm, yes it should, thank you
Last edited by Fusionary; 13-06-2012 at 15:24.
13. Re: How to do this C3 question?
Okay so
Last edited by Fusionary; 13-06-2012 at 15:28.
14. Re: How to do this C3 question?
(Original post by Fusionary)
Okay so
You've gone wrong somewere, it should be 2x-3 in the bracket not 2x-6. It would be much easier to do if you divided everything by -4 then completed the square. You can always multiply by 4 again afterwards to make the numbers easier.
15. Re: How to do this C3 question?
(Original post by Fusionary)
Okay so
16. Re: How to do this C3 question?
17. Re: How to do this C3 question?
(Original post by raheem94)
yes it is, can you post a worked solution in spoiler please?
18. Re: How to do this C3 question?
(Original post by Fusionary)
Okay so

Hence the equation has no real roots, consider the discriminant,

19. Re: How to do this C3 question?
That is correct, now since this is true for all x, can you find the values fo b? What is (2x-3)^2 always bigger than?
20. Re: How to do this C3 question?
(Original post by Fusionary)
yes it is, can you post a worked solution in spoiler please?
I have posted some working, if it doesn't makes sense tell me, so that i can explain it further.