# Post any Core 2 questions that you have here and I will answer them :)

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If you have any Core 2 questions, just post them here and I am will answer them for you with a detailed explanation of how to answer it.

Posted: 14-05-11 11:58 by George

ok I have a question:

Verify that x=2 is a root of the equation, (2x + 5)^4 - (2x - 5)^4 = 3680x - 800

I did it the method of using f(x) where x= 2 which worked as it equalled 0, but the mark scheme showed it just replacing the x in the brackets with 2, I thought you weren't allowed to do this?

Posted: 18-05-11 11:01 by Nicola

I dont see why this a problem, to place the 2 within the brackets, to show that both sides are equal to 0.

Whats your reasoning to behind why it doesnt work?

Posted: 18-05-11 11:45 by George

well what I did was turn it into a cubic, I think I got 320x^3 - 1680x + 800 which cancelled down to 4x^3 - 21x + 10

then put the x = 2 into that

but I didn't think if you get a questions such as (x-3)^2 you cant just put the x in.. or can you?

Posted: 18-05-11 12:12 by Nicola

Firstly how did you turn that into a cubic?

And also there is no need to turn it into anything else. All you have to do is look at what you have and substitute 2 in so that to see if it is a solution

Yeah you can just substitute it in. However there is no point doing it in the example you gave seeing as there is no solution to the question !

Posted: 18-05-11 12:57 by George

Yes there was a previous part to the question which I didn't write which allowed me to turn into a cubic.

Posted: 18-05-11 13:49 by Nicola

Oh okay

Tbh this is a bit of an abiguous question and could answered in many different ways. So I wouldnt worry about it.

In the end of the day you have to pick the style that suits you best

Posted: 18-05-11 16:03 by George

I'll find you a really hard logs question to do as I can't do them at all!

Posted: 18-05-11 18:36 by Nicola

ok :)

a) sketch curve y = 6 multiplied by 5^x stating co-ordinates of any points of intersection with axes

b) point P on curve y = 9^x has co-ordinates equal to 150. Use logs to find x-coordinate of P

c) the curves y= 6 multiplied by 5^x and y=9^x intersect at Q. Show that x-coordinate of Q can be written as

x = 1+logv3 2/ 2-logv3 5

Posted: 18-05-11 18:46 by Nicola

http://getrevising.co.uk/account/resources/logarithms_revision_notes_for_core_2

have a look at this, if you still dont get it message me !

Posted: 18-05-11 19:04 by George

ok I have something else :P

trying to find a and k, usually fine at algebra but I've reached a part the mark scheme can't help me realise..

I've got 4k^3a = 128       and          ak = 2

but the mark scheme goes straight from the first equation to k^2 = 16.. how?! :S

Posted: 19-05-11 20:02 by Nicola

don't worry, worked it out :)

Posted: 19-05-11 20:15 by Nicola

Was this a logarithms questions? Good to know that you worked it out. Sorry I didnt reply, been a bit busy, got an exam tommorow :/

Posted: 19-05-11 20:31 by George

yep same! c2?

Posted: 20-05-11 11:10 by Nicola

no it was D1. Was pretty difficult. Did you do it?

Posted: 20-05-11 16:16 by George

hey how do u answer these two  a surd question s

1. 8√8  is equal to 8 to the power of x . what is x?

2.8√8 can also be written as m√2. what is m?

plzzzzzzzz help  me as i don't really get surds..... reply soon x thnx

Posted: 20-05-11 20:09 by Sheron

Im under the impression that this is a logarithm question as you have to solve for a power.

1. 8√8 = 8^x

log(1. 8√8) = log8^x

log(1. 8√8) = xlog8

x = log(1. 8√8 / log8)

﻿

﻿2.8√8 = 2.8√4√2

﻿2.8√8 = (2.8 x 2)√2

﻿2.8√8 = 5.6√2

Posted: 21-05-11 09:37 by George

nope, I had c2 - was ok, but last questions didn't understand :/

We do stats instead of D1

Posted: 23-05-11 11:03 by Nicola

Oh I do AS Further maths. Would have done the full A level but joined late because I didnt realise I enjoyed maths so muhc.

So I do C1, C2, C3, C4, M1, M2, S1, D1 and FP1 :)

Do you recon you done okay in the exam though?

Posted: 23-05-11 12:44 by George

You'll have to let me know the result you get. I'll let you know what i get as well.

Posted: 23-05-11 12:44 by George