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# OCR MEI - C1 - 13th May 2015 watch

1. Hey all, I'm one of those that'll keep the grade boundaries low for you :P yep there are plenty of us so don't worry.

Just asking because I keep forgetting, for what reasons do you need to work out the discriminant and when the d2y÷dx2? Keep getting it the wrong way round.

Also for the discriminant, is it positive or negative that has 0 or 2 real roots?
2. (Original post by xoharrypotter)
Find the set of values of k for which the graph of y=x^2+2kx+5 does not intersect the x axis.

So did:
b^2-4ac

2k^2-4x1x5<0
2k^2-20<0
2k^2<20
k^2<10
k<root10

According to the markscheme i would of gotten 3/4 but not 4/4 because when you sub in the equation to b^2-4ac you sub 4k^2 not 2k^2

Why would it be 4 and not 2 since 2 is in the equation right?
Thank you
my only issue is how did u get 2k^2-4x1x5 from y=x^2+2kx+5
3. (Original post by Velocity_)
my only issue is how did u get 2k^2-4x1x5 from y=x^2+2kx+5
a=1 b=2k c=5 , so b^2 - 4ac will be (2k)^2 - (4x1x5)
4. [QUOTE=micaela_m;55718741]
Yeah thank you, I'm just doing that paper now, I've done it before but it was a while back. Thanks for your help!! Good luck if you're doing the exam tomorrow
Anytime! Good luck tomorrow ! You'll smash it
5. (Original post by climatechange101)
thank youuuu xxx i really needed some motivation xxx
You'll do great tomorrow! Good luck

Posted from TSR Mobile
6. Good luck tomorrow everyone you'll all do great!
7. Good luck
8. (Original post by Jablonski)
Hey all, I'm one of those that'll keep the grade boundaries low for you :P yep there are plenty of us so don't worry.

Just asking because I keep forgetting, for what reasons do you need to work out the discriminant and when the d2y÷dx2? Keep getting it the wrong way round.

Also for the discriminant, is it positive or negative that has 0 or 2 real roots?

Discriminant b^2-4ac is used to find how many roots a quadratic has (how many times it crosses the x axis)
>0 means 2 real roots
=0 means 1 equal root
<0 means no real roots

You do d^2y/dx^2 to find whether a stationary point (where dy/dx = 0) is a maximum or minimumD^2y/dx^2 > 0 means it is minimum
D^2y/dx^2 < 0 means maximum

Hope this helps
9. (Original post by Brian luiz)
Discriminant b^2-4ac is used to find how many roots a quadratic has (how many times it crosses the x axis)
>0 means 2 real roots
=0 means 1 equal root
<0 means no real roots

You do d^2y/dx^2 to find whether a stationary point (where dy/dx = 0) is a maximum or minimumD^2y/dx^2 > 0 means it is minimum
D^2y/dx^2 < 0 means maximum

Hope this helps
Differentiation is not in C1 is it?
10. (Original post by AlexParmenter)
I can't find the exact question but if you have a circle equation and the equation of a tangent, how do you find the equation of the other parallel tangent? Obviously you have the gradient but what point would you sub in? Thanks
Need to sleep soon so this will be brief
Basically the point A is a number of x and y away from the centre of the circle
so say if x increases by 1 and y increases by 2 (to get A from the centre)
To get B (where there is a parallel tangent to A) you get the centre of the circle and decrease x by 1 and decrease y by 2
11. Good Luck everyone. Hope for a good paper!
12. (Original post by Rik21)
Need to sleep soon so this will be brief
Basically the point A is a number of x and y away from the centre of the circle
so say if x increases by 1 and y increases by 2 (to get A from the centre)
To get B (where there is a parallel tangent to A) you get the centre of the circle and decrease x by 1 and decrease y by 2
Awesome, thanks! Good luck everyone!
13. Advice everyone who panics easily not to come on tsr after the exam last year I did and it affected a lot of my exams after because talking about the answers 😭
14. just done the exam, found it pretty easy tbh. I got the infamous question 12 I unlike most of my friends. your opinions
15. Just sat the paper and it was absolute hell!
Hardest C1 paper I have ever done
16. Found that pretty easy, hopefully got 100% UMS.
17. eh, was okay... think I made a silly mistake on Q6.ii)..the 32 over root 2 one and maybe Q12.i).
Oh well, not bad over all, hopefully high A!
18. 32 over root 2 had to be timed by root two over root two. overall, the paper was easy
19. Went calm probs got 70 or 71 out of 72 lost a mark or 2 on the pesky surd one.
20. and yeah, Q12i was a nightmare

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