Turn on thread page Beta
 You are Here: Home >< Maths

# P1 maths - discriminant/top-up fees watch

1. i think you'll find this a fairly easy question (i say easy because its worth 3 marks) but i'm stuck so please can you explain every step

"given that the quadratic equation

2x^2 + 8x + (k+3) = 0

has equal roots, find the value of the constant k"

thanks
2. if the roots are equal, then b^2 - 4ac = 0
8^2 - (4*2)(k + 3) = 0
64 - 8k + 24 = 0
88 = 8k
k = 11
3. thanks for the help, do you know of any websites that are good for this type of maths (discriminant etc)?
4. (Original post by greenie787)
thanks for the help, do you know of any websites that are good for this type of maths (discriminant etc)?
nope, fraid not. dont you have a p1 textbook?
5. yeah but i'm finding it hard to understand, i get most of the stuff its just this and comparing coeficients
6. (Original post by edders)
if the roots are equal, then b^2 - 4ac = 0
8^2 - (4*2)(k + 3) = 0
64 - 8k + 24 = 0
88 = 8k
k = 11

This may be wrong. I think you should check it. I get k=5.
7. (Original post by greenie787)
yes i just checked the mark scheme and it is 5. can you write up how you did it please?

2x^2 + 8x + (k+3) = 0

b^2 - 4ac = 0 (equal roots)
8^2 - 4.2(k + 3) = 0
64 - 8(k + 3) = 0
64 - 8k - 24 = 0
8k = 40
k = 5.
8. thank you
9. (Original post by Ralfskini)
2x^2 + 8x + (k+3) = 0

b^2 - 4ac = 0 (equal roots)
8^2 - 4.2(k + 3) = 0
64 - 8(k + 3) = 0
64 - 8k - 24 = 0
8k = 40
k = 5.
Yep I can confirm that is correct, k=5
10. what about when the roots are >0 or < 0, is it possible to solve then?

also there is a similar question worth 1 mark asking with a reason to "state the number of real roots of"
x^3 -3x^2+6=0
11. (Original post by Ralfskini)
2x^2 + 8x + (k+3) = 0

b^2 - 4ac = 0 (equal roots)
8^2 - 4.2(k + 3) = 0
64 - 8(k + 3) = 0
64 - 8k - 24 = 0
8k = 40
k = 5.
yes very clever. it was only a small mistake with the signs.
12. (Original post by edders)
yes very clever. it was only a small mistake with the signs.

Forgiven.
13. (Original post by greenie787)
what about when the roots are >0 or < 0, is it possible to solve then?

also there is a similar question worth 1 mark asking with a reason to "state the number of real roots of"
x^3 -3x^2+6=0
>0 means two real different roots.
<0 means no real roots. you can solve it using complex numbers though, but thats beyond alevel.
14. (Original post by edders)
yes very clever. it was only a small mistake with the signs.
Edders do Unis look favourably on you doing a gap year?
15. (Original post by 2776)
Edders do Unis look favourably on you doing a gap year?
i dont think they care either way, tbh
16. (Original post by edders)
i dont think they care either way, tbh
Hmm, ans you arn't bothered about the extra tutition fees that you will be paying?
17. (Original post by 2776)
Hmm, ans you arn't bothered about the extra tutition fees that you will be paying?
im not paying extra tuition fees. im going in 2004.
18. (Original post by edders)
im not paying extra tuition fees. im going in 2004.
Yes, and tution fees are in place by 3006 arn't they? So in 2006 you will be paying an extra year of tuition fee.
19. (Original post by 2776)
Yes, and tution fees are in place by 3006 arn't they? So in 2006 you will be paying an extra year of tuition fee.
for people starting 2006, i believe.
20. (Original post by edders)
for people starting 2006, i believe.
lol, yes sorry.

But arn't teh fees start for 2006 for all people including those who study then as well? So you would pay an extra years of tutition fees if you havnt taken a gap year...

Turn on thread page Beta

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: December 28, 2003
Today on TSR

### He lied about his age

Thought he was 19... really he's 14

### University open days

1. University of Bradford
University-wide Postgraduate
Wed, 25 Jul '18
2. University of Buckingham
Psychology Taster Tutorial Undergraduate
Wed, 25 Jul '18
3. Bournemouth University
Clearing Campus Visit Undergraduate
Wed, 1 Aug '18
Poll
Useful resources

## Make your revision easier

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.