Maths help paper 1 & 6 :D normal distribution :D :D :D

[superduper2009]

Can someone solve the following question for me please ->
MAY/June 09 q 3 for paper 1 i.e. pure maths 1.... with all the working...
Also can you please explain when to use continuity correction and when not to use it for normal distribution in statistics

[astarmathsandphysics]

2 hours

[astarmathsandphysics]

For what paper and board

[superduper2009]

paper 1 cie
thanks in advance

[astarmathsandphysics]

a)(2+3x)^5 =5C0*2^5*(3x)^0+5C1*2^4*(3x)^1+5C2*2^3*(3x)^2=32+240x+720x^2
b)(1+ax)(2+3x)^5 =(1+ax)(32+240x+720x^2)=..+x^2(720+240a)+...
since the x^2 term is 0 720+240a=0 so a=-3

[astarmathsandphysics]

Continuity corrections explained here

http://www.astarmathsandphysics.com/a_level_maths_notes/a_level_maths_notes_s2_menu.html

[superduper2009]

Thank you sooo much..
can you help me with one more thing...
in the same paper...can you please do question number 2 as well...
thanks in advance
+rep

[astarmathsandphysics]

kx-4=x^2 -2x
x^2-(2+k)+4=0
2 distinct points so b^2 -4ac>0
(-(2+k))^2 -4*1*4>0
4+4k+k^2-16>0
k^2+4k-12>0
(k+6)(k-2)>0
k<-6 or k>2

see also

[superduper2009]

That was fast...
Thanks a lot
By the way ur amazing ... and thank you LOADS & LOADS for this amazing website and freeexampapers.com...... they helped me out ... ALOT ...and i really mean ALOT

[astarmathsandphysics]

We try

[superduper2009]

one more quick question
cie october november 2008 paper 6..... question 1
I get the mean...but i get the standard deviation wrong...
can you please explain how to calculate the standard deviation

EDIT
STOP STOP... I GOT IT I WASN'T SQUARING THE MEAN SORRY SORRY  

[astarmathsandphysics]

Use
where

[superduper2009]

thank you sooooooooooooooooooooo much i really really appreciate it

[astarmathsandphysics]

Done now. Every time I try something new with the version of latex on the forum I have to do some pfaffing around