2016 May 25th Edexcel Core 2 Questions and answers. [Unofficial mark scheme] 2016

wait wait when u integrate for area do uhave to have a +C ?

wait wait when u integrate for area do uhave to have a +C ?

wait wait when u integrate for area do uhave to have a +C ?

When you integrate you get = x+c
However when you are trying to find an area for values between a and b
b+c -(a+c) the constants don't change no matter what x is so it's safe to cancel them out instantly.
b-a+c-c = b-a

I calculated my predicted UMS score and I got 234-235 ( from the 2015 grade boundaries), is that still a B.

PDF COPY: http://www.thestudentroom.co.uk/attachment.php?attachmentid=538187&d=1464189347

1 Geometric series question, prove $a=64$ given $S_4=175$ and $r=\frac{3}{4}$ then workout sum to infinity. Then find the difference between the 9th and 10th term

2 Trapezium rule. $y=8-2^{x-1}$ in the interval $[0,4]$ with 4 trapeziums

3 Circle centred at $(7,8)$. Find the equation of it and of a tangent at point $(10,13)$

4 where $f x =6x^3+13x^2-4$ find the remainder when divided by $(2x+3)$ then factorise it fully given $(x+2)$ is a factor.

5 Expansion of $(2-9x)^4$. The using that expand $(1+kx)(2-9x)^4$ in the form $A -232x + Bx^2$ given the coefficient of $x$

6 $1-2\sin(\theta - \frac{\pi}{5})=0$ solve for $\theta$ and $4\cos^2 x + 7\sin x - 2 = 0$

7 This was $\int (3x-x^{\frac{3}{2}}) dx$ and then find the limits (where it crossed the $x$ axis.

8 $\log_3(3b+1)-\log_3(a-2)=-1$, write b in terms of a then find $x$ given $2^{2x+5}-7(2^x)=-1$.

9 Find optimum perimeter of a funny shape which comprised a rectangle, sector and a equilateral triangle, need diagram.
Image by Cake_Chan
Equations given, that needed proving are, $y=\frac{500}{x}-\frac{x}{24}(4\pi+3\sqrt{3})$
and $P=\frac{1000}{x}+\frac{x}{24}(4\pi+36-3\sqrt{4})$


My answers:
1 a) (2 marks) proof
b) (2 marks) $256$
c) (2 marks) $1.602$

2 a) (1 mark) $7$
b) (3 marks) $20.75$
c) (2 marks) $5.75$

3 a) (2 marks) $\sqrt{34}$
b) (3 marks) $(x-7)^2+(y-8)^2=34$
c) (4 marks) $3x+5y-95=0$

4 a) (2 marks) $5$
b) (2 marks) $f(-2)=0$
c) (4 marks) $f(x)=(x+2)(3x+2)(2x-1)$

5 a) (4 marks) $16-288x+1944x^2$
b) (1 mark) $16$
c) (2 marks) $\frac{7}{2}$
d) (2 marks) $936$

6 i) (3 marks) $\frac{8\pi}{15}$or $\frac{-2\pi}{15}$
ii) (6 marks) or

7 a) (3 marks) $\frac{3}{2}x^2-\frac{2}{5}x^{\frac{5}{2}}+c$
b) (3 marks) $24.3$

8 i) (3 marks) $b= \frac{3a-5}{9}$
ii) (4 marks) $-2.19$

9 a) (2 marks) $\frac{\pi x^2}{3}$
b) (3 marks) proof
c) (3 marks) proof
d) (5 marks) $x=16.63$ $P= 120m$
e) (2 marks) $f''x = 0.437 > 0 \therefore$ is a minimum at $x$

This is useful and was spread out over another thread so I thought I would post it here. The missed answers were all either proofs or not suited to a single number response.

for the first part of the logs

I said 1/3 = 3b+1/a-2

then 1/3a -2/3= 3b+1

1/3a-5/3=3b

1/3a-5/3 all divided by 3 = b

Is this correct and how many marks would i lose if incorrect?

I did that too! The difference was negative thiugh so I hope it's right


QUOTE=Fatmanlolololol6;65158247]I am quite pissed. I got full marks in this paper, but for question 1.b. I wrote -1.602. Would that be penalised? And does that mean I can still get full UMS?

For question 8i would this be a valid way to get to the answer?
I did it this way during the exam but everyone I've spoken to seems to have done it a different way.

$log_3(3b+1)-log_3(a-2)=-1$

$log_3(3b+1)+1=log_3(a-2)$

$log_3(3b+1)+log_33=log_3(a-2)$

$log_33(3b+1)=log_3(a-2)$

$3(3b+1)=a-2$

$9b+3=a-2$

$9b=a-5$

$b=\frac{a-5}{9}$

That method looks perfectly fine, i would worry about it aha

I did that too! The difference was negative thiugh so I hope it's right

I am quite pissed. I got full marks in this paper, but for question 1.b. I wrote -1.602. Would that be penalised? And does that mean I can still get full UMS?

I did that too omg thought I was the only one! So the negative value is right

1.b. Is wrong. The answer is -1.602. It has to be negative because in geometric sequence, the biggest term is subtract by the smallest.Therefore 64(3/4)^9 - 64(3/4)^8 = -1.602 (to three decimal places).P.S. I don't know if the markscheme would say 'ignore' signs.