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Edexcel C3 June 2016 - Unofficial Mark Scheme

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1. (Original post by Dieselblue)
Hmm I think i did something stupid in the exam saying that -4x^2+20 = -4(x^2+5) which is wrong. Would I get the final mark for writing the -4x^2+20/(x^2+5)^2 ? Because I definitely wrote that.
I think you would lose an accuracy mark.
2. for the modulus graph i left it as 1/2ln(25/4) for x-cordinate. will i lose marks for not simplifying further?
3. For 8c I only got 2 positive values?
4. can someone show their working for 9c? please reply to this/tag me so I know if you've done it !
5. What was q 8?
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6. (Original post by veldt127)
I'm not 100% sure on all of these, but I think most are correct.

1.
A -5, 6
B 6

2.
A (20-4x^2)/(x^2+5)^2 Might not be simplest form
B >sqrt(5), <-sqrt(5)

3.
A R= sqrt(5)
a= 26.57°
B 33.0°, 273.9°
C 86.1°

4.
Ai 21
ii ln(2.5)
iii 25
B Show that question
C 1.4368, 1.4373
D Show the root was in [1.4365, 1.4375]

5.
i 0.9463
ii 0.5cosec(4Y)

6.
A A=3, B=4
B Normal eqn. -0.5x + 17.5

7.
A graph of arcsin, sort of a rotated S shape. Went through (0,0), (-1,-pi/2), (1,pi/2)
B -1-0.5sqrt(3)

8.
A Trig proof
B -2.848, -1.277, 0.294, 1.865

9.
A 6.740 - dose after 4 hours
B show that dose equalled a value after 7 hours
C 5ln(2 + 2e^-1)
A = 5, B = 2

Sorry about the formatting, I'll try to improve it once I'm home.
Got the exact same!
7. If I put -root5 < x < root 5

Do I get any marks at all??

Im a ****ing spac I dont know why I did that
8. (Original post by Mattematics)
4e^2x - 25 = 0
e^2x = 25/4
e^x = 5/2
x = ln(5/2)
I left it as 0.5ln(25/4). Did they want a simplified form?

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9. (Original post by eyeman567)
What were the equations for F and G
7x-1= f(x)
g(x)= 4/(x-2)
I think
10. (Original post by theereflex)
For 3(c), I don't understand why the lowest value of theta wasn't just 33 from part b?

anyone help?
Same here
11. (Original post by veldt127)
I'm not 100% sure on all of these, but I think most are correct.

9.
A 6.740 - dose after 4 hours
B show that dose equalled a value after 7 hours
C 5ln(2 + 2e^-1)
A = 5, B = 2
for q9 a i got something like 5.1...... and got the 6.7.... for part b. But i managed to prove part b, as the timings were different so different values or nah?.
Did anyone else get 5.1... or so for a??

And I swear this question has appeared before in another C3 paper....
12. (Original post by eyeman567)
If I put -root5 < x < root 5

Do I get any marks at all??

Im a ****ing spac I dont know why I did that
That's what I got

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13. (Original post by Further)
7x-1= f(x)g(x)= 4/(x-2)
I think
Yeah I think it was that, I don't get how you solve it though

I subbed G into F

Got 28 / (x-2) = x + 1

Then ended up with X^2 - x - 30 = 0

which Im pretty sure is wrong and unsolvable
14. (Original post by unimaginable118)
Does anyone remember how many marks the last question was? I was SO STUPID. I left it out (( looks like someones not going to uni...
I did the same, i think it was 8 marks, thought i had done well on time as i finished question 8 as the exam finished and theres normally 8 questions but yeah 😒
15. I though I got 72/75 in this paper, but when I found out that I did a silly mistake in question 3, I don't know if will get an A*.

I said a=tan^-1(2)=63.43...

And I used this value for the rest of question 3. Can I still get can A*?
Same here
3b) denominator was 2cos(theta) - sin(theta) -1,
3c) 2cos(theta)+sin(theta)-1

You need to switch sign for cos(theta+Value)=59....

to cos(theta-Value)=59....
17. Yeah it was definitely 4x^2+20, it looked like you could factorise and cancel out an x^2+5 but you couldn't because of the negative sign in front of the x^2 at the top
18. How many marks was question 6b out of?
19. (Original post by Dieselblue)
For 5i what did people do with the sin and cos?

Also part 2a is wrong, -4x^2-20=-4(x^2+5) so -4/x^2+5
I am sorry but you might have got the answer wrong
20. (Original post by ravichauhan11)
nope it was 20-4x^2. not -20-4x^2. there was no further cancellation
Agreed.

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