# 2017 Maths Edexcel C3 Unofficial Mark Scheme

Announcements Poll: How many marks do you think you got?
0-30 (106)
4.25%
31-35 (50)
2%
36-40 (77)
3.09%
41-45 (106)
4.25%
46-50 (154)
6.17%
51-55 (318)
12.75%
56-60 (354)
14.19%
61-65 (467)
18.72%
66-70 (477)
19.12%
71-75 (386)
15.47%
#1
1. 2/(x-3)

2a. x=3+ln2

b. y=(4e^2-5)/(e^2+2)

3a. g(x)>=3

b. g^-1(x)=(x-3)^2-2, x>=3

c. x=(7+sqrt21)/2

d. a=(7+sqrt21)/2

4a. R=sqrt29 alpha=0.3805(awrt 0.381)

b. 5cos2x-2sin2x=3

c. x=0.30 or 2.46

5a. 2x+5y=11

c. x2=1.9950 x3=1.9929

6ai. V-shaped x-int=a/2 y-int=a

ii. V-shaped y-int=a+b

b. c=4a

7ia. dydx= 2(11x^2-1)(x^2-1)^4

b x>=1 or x<=1 EDIT : Answer is actually x>=1/sqrt(11) or x <= -1/sqrt{11} (see here for confirmation - scroll down for solutions)

ii.dydx= 1/[2sqrt(e^2x+1)] EDIT : This should be 1/[2sqrt(e^(2x)-1)]

8a.65

b. [10^-0.1t(24e^-0.9t-1)]/(1+3e^-0.9t)^2

ci. T=3.53 ii. 102

d. 40

9b. 0, 16.3, 163.7, 180

22
4 years ago
#2
Alpha was 0.381 I think, 3 dp
11
4 years ago
#3
for question 8 i think, i got something like T=3. something and P =102 and k=40
5
4 years ago
#4
(Original post by KloppOClock)
for question 8 i think, i got something like T=3. something and P =102
3.3 something and 104 here.
1
4 years ago
#5
I need answer for the last 3 questions only.
1
4 years ago
#6
Probably like 65 for an A* as it wasn't the easiest paper.
10
#7
7ia. dydx= 2(11x^2-1)(x^2-1)^4
b x>=1 or x<=1
ii.dydx= 1/[2sqrt(e^2x+1)]
8a.65
b. [10^-0.1t(24e^-0.9t-1)]/(1+3e^-0.9t)^2
ci. T=3.53 ii. 102
d. 40
9b. 0, 16.3, 163.7

I might be wrong lmao

Posted from TSR Mobile
1
4 years ago
#8
C=4a/7 isnt it?
21
4 years ago
#9
Anyone else get c in terms of a as 2a
18
4 years ago
#10
(Original post by gnehcnosna)
7ia. dydx= 2(11x^2-1)(x^2-1)^4
b x>=1 or x<=1
ii.dydx= 1/[2sqrt(e^2x+1)]
8a.65
b. [10^-0.1t(24e^-0.9t-1)]/(1+3e^-0.9t)^2
ci. T=3.53 ii. 102
d. 40
9b. 0, 16.3, 163.7

I might be wrong lmao

Posted from TSR Mobile

180 for 9B as well (btw just a suggestion, would it be better if you updated the post at the beginning so people can see? cheers)
2
4 years ago
#11
(Original post by gnehcnosna)
1. 2/(x-3)
2a. x=3+(ln8)/3
b. y=(4e^2-5)/(e^2+2)
3a. g(x)>=3
b. g^-1(x)=(x-3)^2-2, x>=3
c. x=(7+sqrt21)/2
d. a=(7+sqrt21)/2
4a. R=sqrt29 alpha=0.3805
b. c=3
c. x=0.30 or 2.46
5a. 2x+5y=11
c. x2=1.9950 x3=1.9929
6a. V-shaped x-int=a/2 y-int=a
b. V-shaped y-int=a+b
b. c=4a

Posted from TSR Mobile
2. You could simplify :1/3ln 8 = ln2

And 4b required 2dp.

Other than that it's all good.
1
4 years ago
#12
Also t=3.53 pmax=102(Before u reply it said integer in q) also k=40 and last q sin=-1/2 and 0 cant remember other value
0
4 years ago
#13
(Original post by Kowalifwer)
C=4a/7 isnt it?
That's what I got. Not sure though
1
4 years ago
#14
(Original post by gnehcnosna)
7ia. dydx= 2(11x^2-1)(x^2-1)^4
b x>=1 or x<=1
ii.dydx= 1/[2sqrt(e^2x+1)]
8a.65
b. [10^-0.1t(24e^-0.9t-1)]/(1+3e^-0.9t)^2
ci. T=3.53 ii. 102
d. 40
9b. 0, 16.3, 163.7

I might be wrong lmao

Posted from TSR Mobile
Please edit this into your first post. Try to read replies and look for a consensus and change your answers if you think they're wrong. Thanks 0
4 years ago
#15
(Original post by gnehcnosna)
7ia. dydx= 2(11x^2-1)(x^2-1)^4
b x>=1 or x<=1
ii.dydx= 1/[2sqrt(e^2x+1)]
8a.65
b. [10^-0.1t(24e^-0.9t-1)]/(1+3e^-0.9t)^2
ci. T=3.53 ii. 102
d. 40
9b. 0, 16.3, 163.7

I might be wrong lmao

from TSR Mobile
I got the same answer for 8a 8d and 9b. 8b i cant remember.
0
4 years ago
#16
9) sinx = -3+root17/4
16.3, 163.7
7
4 years ago
#17
What did everyone get for the question that was:
"Given x = ln(sec(2y)), work out dy/dx as a function of x"
I got 1/(2(e^x)sin(arccos(1/(e^x))))
Since dx/dy is 2tan(2y), we know that dy/dx = 1/(dx/dy) = 1/2 * cot(2y). We also can rearrange x to get y=
x = ln(sec(2y))
e^x = sec(2y)
1/(e^x) = cos(2y)
y = arccos(1/(e^x)) / 2
Which we then sub in as
1/2 * cot(arccos(1/(e^x)))
Which gets us to
1/2 * (cos(arccos(1/(e^x))) / sin(arccos(1/(e^x)))
Which is then
1/(2(e^x)sin(arccos(1/(e^x))))

Not sure if I've oversimplified (or undersimplified), but that's what I got.
2
4 years ago
#18
(Original post by Cheryl_Yuen)
9) sinx = -3+root17/4
16.3, 163.7
That is exactly what i got. Yesssssssssss
1
4 years ago
#19
That paper was waaaaaavvvvvyyyyy
9
4 years ago
#20
(Original post by Kowalifwer)
C=4a/7 isnt it?
did you take the positive or the negative values from the modulus? my friend took the negative ones and got 4/7a as well, I took the positives and got 4a. dunno which one's correct.
4
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