You are Here: Home >< Maths

# Can someone help me with this question? (further maths) watch

1. The curve with equation y=ax^2+bx+c passes through the points P(2,6) and Q(3,16), and has a gradient of 7 at the point P. Find the values of the constants a, b, and c.

Help would be much appreciated
2. When x = 2, what does y equal? So what must a2^2 + 2b + c equal?
Similarly for x =3.
Also, at x=2, what does dy/dx equal. So ...
3. (Original post by DFranklin)
When x = 2, what does y equal? So what must a2^2 + 2b + c equal?
Similarly for x =3.
Also, at x=2, what does dy/dx equal. So ...
I'm still quite confused
I've worked out that 4a+2b+c=6 and 9a+3b+c=16 but now what? dy/dx when x=2 is 7 but I dont know what to do with that information
4. Well, if y = ax^2+bx+c, then what is dy/dx?
5. Differentiate the equation with the unknowns and sub in the appropriate 'x' value, what should that equal to?
6. (Original post by DFranklin)
Well, if y = ax^2+bx+c, then what is dy/dx?
so dy/dx=2ax+b, when x=2 dy/dx=4a+b so 4a+b=7 ???
7. Yes. So you now have 3 equations in 3 unknowns, which is enough to solve for a, b and c. (Start by noting that b = 7-4a, so you can replace b by (7-4a) in the two other equations).
8. (Original post by DFranklin)
Yes. So you now have 3 equations in 3 unknowns, which is enough to solve for a, b and c. (Start by noting that b = 7-4a, so you can replace b by (7-4a) in the two other equations).
Thankyou that makes a lot more sense now... I'm very new to a-level maths :P
9. (Original post by looloo59)
(Original post by DFranklin)
Yes. So you now have 3 equations in 3 unknowns, which is enough to solve for a, b and c. (Start by noting that b = 7-4a, so you can replace b by (7-4a) in the two other equations).
Thankyou that makes a lot more sense now... I'm very new to a-level maths :P
Okay.. so maybe not so much sense. I've got confused again
10. (Original post by looloo59)
Okay.. so maybe not so much sense. I've got confused again
which part?
11. Now secretly glad that i decided agaisnt choosing further maths....
12. (Original post by Pixie_95)
Now secretly glad that i decided agaisnt choosing further maths....
This question appears to be from C1, which is simply 'normal' maths and not further maths.
13. (Original post by Farhan.Hanif93)
This question appears to be from C1, which is simply 'normal' maths and not further maths.
Oh..well now slightly regretting choosing maths, better start revising from now
14. Well I think I have an answer now... y=3x^2-5x+4
still not convinced I'm right but atleast I've got somewhere with it

And the questions was taken from a further maths paper

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: March 25, 2011
Today on TSR

Get the low down

### University open days

• University of Exeter
Wed, 24 Oct '18
Wed, 24 Oct '18
• Northumbria University
Wed, 24 Oct '18
Poll
Useful resources

### 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