Edexcel C2 20th May 2015 Official Thread

In the first line they are splitting up that power to get 1^ x / 3^x and 1^x = 1 so it's just 1/3^x. They then multiply both sides by 3^x.
This gives 1 = 2 * (3^x) * (3*x)
We then divide by two to get (3^x)^2 = 1/2
we then take log of both sides and bring down the power 2x to get 2xlog(3)=log(1/2).
We then divide by log3 to get 2x = log(1/2) / log(3) and then divide by 2 to get the final answer

Thankss

Reply 1661

usmanzubair

3

Good luck guys. :biggrin:

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Reply 1662

frozo123

12

Original post by jshep000

Hopefully, will be bless if we don't get one of those crappy weird questions at the end haha.

probably will unfortunately haha

Reply 1663

ImJared

1

Original post by jshep000

It still works, it just gives you a negative value. Our teacher taught it to us, that if r>1 than we had to swap it and do r-1.

It won't give a negative value (unless the terms are negative) as the denominator is swapped as well. As you can see in the proof, the two formulae give the exact same answer and they are purely conjugates for ease of use:

(edited 8 years ago)

Reply 1664

Skygon

1

Just out of curiosity, when a given range for trigonometric questions, includes >= or <=, do we include the values they're equal to as angles? Like 0 <= x <= 180, is 180 included as an answer? :K:

Reply 1665

Da Di Doo

19

What is an A for the June 2013 R paper?

Reply 1666

ImJared

1

Original post by Skygon

Just out of curiosity, when a given range for trigonometric questions, includes >= or <=, do we include the values they're equal to as angles? Like 0 <= x <= 180, is 180 included as an answer? :K:

Yes, because it means "less than or equal to 180" and not "less than 180".

0 \leq x \leq 180 \equiv \text{values of }x\text{ from 0 to 180 (inclusive)}

(edited 8 years ago)

Reply 1667

alexneuty

3

Original post by coefficient

Because sometimes if we start in year 2000, it's easier to call that year 0 than year 1. Really it's just people who are more confident saving time. There's no real benefit of it, it's just being fancy.

Or just do what I do and count the value of n on your finger if you are confused as to what n might be and use ar^(n-1). Haha I know we went past finger counting at primary school but it still helps to avoid confusion.

Reply 1668

Abbey.

1

Original post by TrentL

thank you very much Abbey and yes that would be amazing!

took me a while :/

Someone please help me on question 7?! https://c4a3f001dcd45afe69d0ceec83003f9fbc283b2c.googledrive.com/host/0B1ZiqBksUHNYSGtmV3dzVVVvNTg/Mock%20QP%20-%20C2%20Edexcel.pdf
Thanks! (also please could you show all your working as to how you got the answer if possible)

Reply 1670

TeeEm

19

Original post by Da Di Doo

What is an A for the June 2013 R paper?

64 for an A
57 for a B

Reply 1671

Lynku555

1

goodnight people. best of luck tomorrow!

Reply 1672

coefficient

1

we get 1 , n, nc2, nc3, for the ncr coefficients and then accending powers of kx.

[br](1+kx)^n = 1 [br]1 n nc2 nc3[br]1 kx k^2 x^2 k^3 x^3[br][br]so overall 1 + nkx + (nc2)k^2 x^2 + (nc3)k^3 x^3[br][br]ncr = n!/(n-1)![br]nc2 = n(n-1)/2[br]nc3= n(n-1)(n-2)/3x2[br]

If the coefficient of

x^2 and x^3

are equal then:

[br]n(n-1)/2 * k^2 = n(n-1)(n-2)/6 *k^3

1/2 = (n-2)/6 * k
3 = k(n-2)

Reply 1673

Supermanxxxxxx

5

Any tips on circles at all

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Reply 1674

jshep000

15

I reckon the paper will be quite chill tbh, C1 had some strange worded questions for some people. So they probably were nice and gave us a good C2 paper <3