OCR Maths C1 16/05/12 (not MEI)

For the last question, the discriminant was -76 right, so therefore the line doesn't intersect the circle?

For the last question, the discriminant was -76 right, so therefore the line doesn't intersect the circle?

I thought it was pritty hard.

Then again, I can't spell

I did not use the discriminant as you were suppost to work it out algerbically, but I'm sure you worked it out in your own way

I didn't know any other way, so the discriminant ftw!

I did not use the discriminant as you were suppost to work it out algerbically, but I'm sure you worked it out in your own way

You were supposed to sub y=2x into the equation of the circle, then simplify. So you get an quadratic equation in x.

Then, you use the discriminant (b^2 -4ac) of the formula and sub the coefficients in. You get -78 (or whatever it was)

Then you state something like 'discriminant < 0, therefore there are no points of intersection/ no real roots)'

At least that's what I did. I hope I got full marks for it.

I did not use the discriminant as you were suppost to work it out algerbically, but I'm sure you worked it out in your own way

using the discriminant after substituting in y is algebraic.

Copying this over from the other C1 thread

1 x3 -6x2 -11
2 i) k=1/4
ii) k= -3/2
iii) k= 24
3
4 i) 2(x-5)2 -1
ii) minimum point = (5, -1)
5 i) graph
ii) a translation of 4 units in the positive x direction
iii) y = square root (1/5 x)
6 Normal to the curve = 4x -6y -29 =0
7 16+6 root 7, 16- 6 root 7 (16+- 6 root 7)
8 i)stationary point is at (-2, -48)
ii) this is a minimum
iii) x3 + 4 increase as x increases when x> -2
9 i) 0 < x < 4 (length can't be negative)
ii) 1.4 < y < 4.8
10 i) centre (5, -2), Diameter = 10
ii) y = 2x -12
iii) length CP = root 20, P is inside the Circle
iv) y=2x doesn't meet the circle because b2-4ac=-76 < 0

For question 3... (10/3,-2) I think... don't quote me on that, it's off the top of my head

Am I actually duplicating posts from two nearly identical threads hahaha. Crazy crazy crazy world.

Does anyone remember the question for 9i)? And how many points was it worth?

I got that for q3 so looks hopeful