GCSE Question
Maths exam discussion - share revision tips in preparation for GCSE, A Level and other maths exams and discuss how they went afterwards.
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GCSE QuestionQ1. rearange S=2pidsqrthh^2+d^2 i need to make h the subject.
so far i've got s^2=(2pid)^2 (h^2+d^2)
i'm not sure if i'm doing it correctly.
Q2. solve the equation
7/x+2 + 1/x-1 = 4
so far i've got
7x-7 = 4x^2+4x-8 then 4x2-3x-1=0
factorised it
-3+or-(sqrt3^2-4x4x-1)/8
i got x = 0.25 or -1 which i think is wrong.
Q3. bag contains 6 red disks, 4 blue disks and 5 green disks.
A fair dice has 4 red faces and 2 blue faces.
a disk is taken at random from bag and the colour is recorded.
then dice is thrown twice and each time colour of face it lands on is recorded.
work out probability that, of the three colours that are recorded, exactly 2 are the same.Last edited by non; 19-06-2012 at 22:51. -
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Re: GCSE Questioni'm not sure sorry.(Original post by Mrbawby)
For question two wouldn't you * the botoms by eachother -
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Re: GCSE QuestionYou have to multiply the 4 by (x-1)(x+2) too.(Original post by Mrbawby)
7/x+2+1/x-1=4
(x-1). (x+2)
(7x-7)+(x+2)/(x+2)(x-1)=4
7x-7=4x-4
7x=4x+3
3x=3
X=1
Btw i havent started unit 2 so it may be wrong
And you can't cancel out (x+2) in the lines in bold
Last edited by usycool1; 20-06-2012 at 20:24. -
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Re: GCSE QuestionAh, I see. You have to multiply the 4 by (x-1)(x+2) too(Original post by Mrbawby)
Nope, i *7 by x-1 and 1 by x+2 buy like i said i may be wrong
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Re: GCSE QuestionI'll post a different example and you guys can try the original question on your own(Original post by Mrbawby)
Uh you sure 7(x-1)+1(x+2)/x^2+x-2=4 right? Mind doing the question for us
Spoiler:Show
Multiply everything by (x+7)(x+4):
![1(x+4)+3(x+7)=2[(x+7)(x+4)]](http://www.thestudentroom.co.uk/latexrender/pictures/de/de781d5117af304bb35690c4675de385.png "1(x+4)+3(x+7)=2[(x+7)(x+4)]")
Simplify it:
![x+4+3x+21=2[x^2+4x+7x+28]](http://www.thestudentroom.co.uk/latexrender/pictures/cd/cd6235161cd7e98995c8c43f12f50beb.png "x+4+3x+21=2[x^2+4x+7x+28]")
![4x+25=2[x^2+11x+28]](http://www.thestudentroom.co.uk/latexrender/pictures/e6/e645e65dde828862acbfc1c8575325ec.png "4x+25=2[x^2+11x+28]")
Rearrange the equation to get 0 on one side:
It can't be factorised, so use the quadratic formula to get:
OR 
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Re: GCSE Questionthanks i think i've got it. 0.95 and -1.70(Original post by usycool1)
I'll post a different example and you guys can try the original question on your own
Spoiler:Show
Multiply everything by (x+7)(x+4):
Simplify it:
Rearrange the equation to get 0 on one side:
It can't be factorised, so use the quadratic formula to get:
OR
