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Author Topic: IGCSE Maths doubt(paper 4)  (Read 14203 times)

Offline Ghost Of Highbury

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Re: IGCSE Maths doubt(paper 4)
« Reply #15 on: October 31, 2009, 07:09:00 am »
Quote from: ~Alpha on October 31, 2009, 07:04:00 am

Simplified, isn't it x > 2 ???

non..ofcourse not..it is <=4 rite..
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Offline ~~~~shreyapril~~~~

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Re: IGCSE Maths doubt(paper 4)
« Reply #16 on: October 31, 2009, 08:15:38 am »
i think sameer's ans is rite??

dude try picking up ur phone!!


calling from 1 hr!!
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Alpha

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Re: IGCSE Maths doubt(paper 4)
« Reply #17 on: October 31, 2009, 10:33:57 am »
Quote from: A@di on October 31, 2009, 07:09:00 am
non..ofcourse not..it is <=4 rite..



x is greater or equal to 4... See well.
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Offline Ghost Of Highbury

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Re: IGCSE Maths doubt(paper 4)
« Reply #18 on: October 31, 2009, 11:02:01 am »
Quote from: ~Alpha on October 31, 2009, 10:33:57 am


x is greater or equal to 4... See well.

u see well...its x is less than or equal to 4
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Offline ~~~~shreyapril~~~~

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Re: IGCSE Maths doubt(paper 4)
« Reply #19 on: October 31, 2009, 11:05:31 am »
baapre!!!
still that question been discussed!!
read the previous posts clealy!!!

man!!

By the way sorry for being too rude!!!
« Last Edit: October 31, 2009, 11:08:29 am by ~~~~shreycool~~~~ »
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Alpha

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Re: IGCSE Maths doubt(paper 4)
« Reply #20 on: October 31, 2009, 01:31:37 pm »
Ah yes...


x is between 2 and 4 or equal to 4...  I misplaced the order... 2 < x <= 4


I guess am owing them   :P

My excuses....  :)
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Offline ~~~~shreyapril~~~~

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Re: IGCSE Maths doubt(paper 4)
« Reply #21 on: October 31, 2009, 01:33:03 pm »
ya the ans is now correct!!
By the way u taken add. math or not??

just to ans my doubts!!
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Alpha

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Re: IGCSE Maths doubt(paper 4)
« Reply #22 on: October 31, 2009, 02:02:36 pm »
Add Maths... yea.


Hey... what doubts??  :P
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Offline ~~~~shreyapril~~~~

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Re: IGCSE Maths doubt(paper 4)
« Reply #23 on: October 31, 2009, 02:03:45 pm »
7 The position vectors of points A and B, relative to an origin O, are 2i + 4j and 6i + 10j respectively.
The position vector of C, relative to O, is ki + 25j, where k is a positive constant.
(i) Find the value of k for which the length of BC is 25 units. [3]
(ii) Find the value of k for which ABC is a straight line. [3]

l\just the last part!!!

rest is easy!!!
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nid404

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Re: IGCSE Maths doubt(paper 4)
« Reply #24 on: October 31, 2009, 02:13:52 pm »
I don't take add math as yet......but anyway can u put the answer up....so I can crosscheck...I will know if  am doing it correctly
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Alpha

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Re: IGCSE Maths doubt(paper 4)
« Reply #25 on: October 31, 2009, 02:23:55 pm »
Quote from: ~~~~shreycool~~~~ on October 31, 2009, 02:03:45 pm
7 The position vectors of points A and B, relative to an origin O, are 2i + 4j and 6i + 10j respectively.
The position vector of C, relative to O, is ki + 25j, where k is a positive constant.
(i) Find the value of k for which the length of BC is 25 units. [3]
(ii) Find the value of k for which ABC is a straight line. [3]

l\just the last part!!!

rest is easy!!!


If ABC is a str. line,

     AB = hBC, where h is a constant.

AB= OB- OA

BC = OC - OB

Continues in the attachment... I allways have problem explaining answers here... Formatting is confusing... Anyway, see the attachment.
« Last Edit: October 31, 2009, 02:26:55 pm by ~Alpha »
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nid404

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Re: IGCSE Maths doubt(paper 4)
« Reply #26 on: October 31, 2009, 02:35:01 pm »
the 2nd part is right....even I got 16 using gradient formula......should the first 1 be found using th distance formula....i dunno...im askin cuz i didn't take add math for my igs...
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Offline Ghost Of Highbury

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Re: IGCSE Maths doubt(paper 4)
« Reply #27 on: October 31, 2009, 03:00:39 pm »
Quote from: ~~~~shreycool~~~~ on October 31, 2009, 02:03:45 pm
7 The position vectors of points A and B, relative to an origin O, are 2i + 4j and 6i + 10j respectively.
The position vector of C, relative to O, is ki + 25j, where k is a positive constant.
(i) Find the value of k for which the length of BC is 25 units. [3]
(ii) Find the value of k for which ABC is a straight line. [3]

l\just the last part!!!

rest is easy!!!

ok..

first. --> AB=OB - OA = 4i + 6j

--> BC = OC - OB = (k-6)i + 15j

BC = x(AB)

(k-6)i + 15j = 4xi + 6xj

k-6 = 4x
6x = 15

x = 2.5

--

k-6 = 4*2.5 = 10

therefore --> k =16

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nid404

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Re: IGCSE Maths doubt(paper 4)
« Reply #28 on: October 31, 2009, 03:05:01 pm »
why can't u use distance formula here ???
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Offline Ghost Of Highbury

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Re: IGCSE Maths doubt(paper 4)
« Reply #29 on: October 31, 2009, 03:10:29 pm »
Quote from: ~Alpha on October 31, 2009, 02:23:55 pm

If ABC is a str. line,

     AB = hBC, where h is a constant.

AB= OB- OA

BC = OC - OB

Continues in the attachment... I allways have problem explaining answers here... Formatting is confusing... Anyway, see the attachment.


@nid - show how did u use the distance formula?

-----
BC = k-6)i + 15j

sqrt((k-6)^2 + 15^2) = 25

therefore

(k-6)2 = 252 - 152 = 400

k-6= sqrt(400) = 20

hence, k = 26
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