# 2017 OCR C1 official thread - 17th May

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Original post by MohAhmedR
Was the last question 6y+x-51
Was k 81 or 9/4

I got 81 the 1st time but it's wrong because the gradient of the line is 2k/27 but it said the the gradient of the normal is parallel to the other line. So NOT the gradient of the original line.

SO 27/2k (gradient of the normal) = 6 and then you just solve for k which is 9/4
[QUOTE="Boomburst;71500484"]I literally spent 30 mins debating with myself as to whether k was 81 or -27/12 (-9/4). But I don't think I did that bad, could've gone worse!

I ended up with k = -27/12[/QUOTE

How i think it goes...
Original post by jhuk510
Omg someone else put that! Thank god!

Yes, we have a chance

You me and bulletzone put that answer
Original post by Luca715
no, i accidentally replied to the wrong thread, but for the k question i differentiated with repsect to x, made x equal to -3 and the gradient equal to 6 , and i got k=81

The equation of the line they gave was parallel to the normal which is perpendicular to the tangent of the curve. So 6 should become -1/6.

I got that k/x^2 when put in to indices form is kx^-2. This differentiated turns into -2kx^-3.

-2kx^-3=-1/6 substitute x=-3
-2k(-3)^-3=-1/6
-2k x -1/27=-1/6
-2k =9/2
k= -9/4

At least that is what i did
Original post by Chichaldo
My friend did that and realised it was wrong also and changed it. Meant to use the negative reciprocal of the gradient.

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same g
What did everyone get for the turning points question on the differentiation question, and the one where you had to find the turning point and the axis intercept from the complete the square equation?!
gautham here, how did everyone do? pm me on facebook
I still think k=81 for the reason that it says: the normal to the curve is parallel to the line y=4+6x. If its parallel there HAS to be equal gradients. So when you dy/dx the equation and sub x=-3, I think that dy/dx=6. NOT -1/6 as the normal is parallel to the line.
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Original post by ferianjay
I got c=-12, an area of 17/2 or 8.5 and k=-9/4.

I really wasn't confident about my value of k (since when do they use non-integer values?), but as long as I read the question right (the NORMAL to the curve being parallel to the straight line i.e. having a gradient of 6), a quick sketch reveals that k must be negative (and is probably small), so +81 is bunk (as long as I read it correctly).

What did people get for the odd transformation? I think I got a stretch with scale factor 3(root5)/2 parallel to the y-axis. I wasn't happy about that one either.

i said that it was a stretch of SF 1.5 from x axis then a stretch of SF 1/5 from y-axis
k=9/4 i think
Where the **** is the unofficial mark scheme?
Original post by Audrius.C
I still think k=81 for the reason that it says: the normal to the curve is parallel to the line y=4+6x. If its parallel there HAS to be equal gradients. So when you dy/dx the equation and sub x=-3, I think that dy/dx=6. NOT -1/6 as the normal is parallel to the line.
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It's meant to be the curve. 6 is the gradient of the normal, but to the curve it's -1/6. The k is in the equation of the curve
Original post by Audrius.C
I still think k=81 for the reason that it says: the normal to the curve is parallel to the line y=4+6x. If its parallel there HAS to be equal gradients. So when you dy/dx the equation and sub x=-3, I think that dy/dx=6. NOT -1/6 as the normal is parallel to the line.
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When you differentiate you're finding the gradient of the tangent at a particular point. The normal is perpendicular to the tangent so 6 should become -1/6 to get the gradient of the tangent at the point x=-3.
Original post by VictiniCup
Where the **** is the unofficial mark scheme?

Someone is trying to make one on another thread but it's a bit messy as people are just giving answers to questions they can remember.
For the graph transformation question, I got stretch by a scale factor of 4/45 parallel to x-axis. Anyone else?:/

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i got 17/2 so you're clearly wrong. I took the C1 paper last year but only got 99 UMS so I'm retaking to get the 100 I deserve. Geniuses don't accept mediocracy just like I don't accept your answer
. I got the same answer, but on a side note anyone who calls themselves a genius is an egotistical prick.
Original post by tbalysz
What did everyone get for the Rhombus question?

Did u do this specific exam? I don't remember there being a Rhombus question? (Maybe there was and I didn't realise but I don't think I did one)
Original post by ExamsCry
For the graph transformation question, I got stretch by a scale factor of 4/45 parallel to x-axis. Anyone else?:/

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I got 2/15 stretch in x, initially I got stretch 1/5 in x and stretch 2/3 in x, then I wasn't sure on this step but I multiplied these values to get overall stretch of 2/15 in x
Original post by Lol1029
55/56

Last year was something like 52 so I'm putting money on 50
For Q11 I got -27/12 but didn't simplify to -9/4, will I be marked down? I believe I also carried on using -27/12 in part 2
Original post by Jasminea
Did u do this specific exam? I don't remember there being a Rhombus question? (Maybe there was and I didn't realise but I don't think I did one)

Original post by Jasminea
Did u do this specific exam? I don't remember there being a Rhombus question? (Maybe there was and I didn't realise but I don't think I did one)

Lmao he was in another world.