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Author Topic: IGCSE MATHS DOUBTS HERE !!!!  (Read 40472 times)

Offline astarmathsandphysics

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #105 on: January 20, 2011, 10:44:10 pm »
sod him then
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Offline SauD~

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #106 on: January 21, 2011, 10:58:46 am »
Can anyone tell me how to solve questions like 20(b)(i)  :-[
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Offline The Golden Girl =D

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #107 on: January 21, 2011, 11:27:25 am »
Quote from: SimoN on January 21, 2011, 10:58:46 am
Can anyone tell me how to solve questions like 20(b)(i)  :-[

It's Alright with LOADS of practice you'll get the hang of it. :D

(x-3)2

is the SAME as (x-3)(x-3)

the easiest way is to follow this Rule :

(a-b)2

a2 - 2ab + b2

(x-3)2

x2 - 2(x*-3) + (3)2

x2 + 6x + 9

or the long method which is ;

(x-3) (x-3)

x2 -3x -3x +9

x2 -6x + 9 :)
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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #108 on: January 21, 2011, 11:38:35 am »
Quote from: SimoN on January 21, 2011, 10:58:46 am
Can anyone tell me how to solve questions like 20(b)(i)  :-[

How long ago did you start your IGCSE course ?

When are your real IGCSEs ?
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Offline SauD~

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #109 on: January 21, 2011, 11:40:52 am »
Quote from: ~ The Golden Girl ~ on January 21, 2011, 11:27:25 am
It's Alright with LOADS of practice you'll get the hang of it. :D

(x-3)2

is the SAME as (x-3)(x-3)

the easiest way is to follow this Rule :

(a-b)2

a2 - 2ab + b2

(x-3)2

x2 - 2(x*-3) + (3)2

x2 + 6x + 9

or the long method which is ;

(x-3) (x-3)

x2 -3x -3x +9

x2 -6x + 9 :)
no no Nuna i knew that ;D
the question below that one... never have done that in class ;D

Tomorrow is the exam... and i did the past paper i got 66/70 :D
only because of that and some silly mistakes :D
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Offline Amii

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #110 on: January 21, 2011, 12:00:07 pm »
By the method of completing the square

x2-6x + 10
=(x-3)2 -32 +10
=(x-3)2 +1

hence p=3 and q =1
« Last Edit: January 21, 2011, 12:03:44 pm by Amii »
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Offline SauD~

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #111 on: January 21, 2011, 12:09:37 pm »
Quote from: Amii on January 21, 2011, 12:00:07 pm
By the method of completing the square

x2-6x + 10
=(x-3)2 -32 +10
=(x-3)2 +1

hence p=3 and q =1
where did 6x turned it only 3 ???
help! can you explain :(
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Offline Amii

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #112 on: January 21, 2011, 12:21:03 pm »
Quote from: SimoN on January 21, 2011, 12:09:37 pm
where did 6x turned it only 3 ???
help! can you explain :(
That's the way you half it  :D

x2-ax+b
=(x-1/2a)2 - (1/2a)2 + b

x2+ax+b
=(x+1/2a)2 - (1/2a)2 + b

You want me to give you some example questions to solve?
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Offline Arthur Bon Zavi

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #113 on: January 21, 2011, 12:24:28 pm »
Quote from: SimoN on January 21, 2011, 12:09:37 pm
where did 6x turned it only 3 ???
help! can you explain :(

There's one formula to solve these type of sums, but will be covered in AS Levels (Pure Mathematics 1)

Equation will be in the form x2 + bx + c = 0

(x + 1/2b)2 = x2 + bx + 1/4b2, so x2 + bx  = (x + 1/2 b)2 - 1/4b2

Adding c to both the sides will give :

x2 + bx+ c = (x2 + bx) + c = { (x + 1/2b)2 - 1/4b2 } + c

I do this way :

x2-6x + 10
(x2 - 6x + 9 + 1)
(x - 3)2 + 1

Therefore, p=3 and q = 1
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Offline SauD~

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #114 on: January 21, 2011, 12:30:45 pm »
i know i got some simple and stupid,
but where did the x go, we can't just remove the x as we don't know the value :-[
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Offline Arthur Bon Zavi

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #115 on: January 21, 2011, 12:37:51 pm »
Quote from: SimoN on January 21, 2011, 12:30:45 pm
i know i got some simple and stupid,
but where did the x go, we can't just remove the x as we don't know the value :-[

You know what ! You can REMOVE whatever you want.

BUT

then you will not know when examiner will REMOVE the marks. :P
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Offline SauD~

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #116 on: January 21, 2011, 12:40:43 pm »
Quote from: Fidato on January 21, 2011, 12:37:51 pm
You know what ! You can REMOVE whatever you want.

BUT

then you will not know when examiner will REMOVE the marks. :P
i will call my mommy, because this big guy is bullying :'( :'(
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Offline Amii

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #117 on: January 21, 2011, 12:43:19 pm »
x2-6x + 10
=(x-3)2 -32 +10

Look it will be the same thing when you solve it
=(x-3)2 -32 +10
=(x2 - (2*3*x)+32) -32 +10
=x2- 6x + 9 -9 + 10
=x2- 6x +0 + 10
=x2 -6x +10
Again you are getting back the same thing right?
Now disappearing of x is okay?  :P
« Last Edit: January 21, 2011, 12:50:05 pm by Amii »
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Offline SauD~

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #118 on: January 21, 2011, 12:54:26 pm »
(x-3)2 - 32 +10 would be:
(x-3)(x-3) - 9 + 10
x2 -3x-3x +9 + 1
then:
x2 -6x + 10

:o :o :o :o
i got it :D :D :D :D
1st factorize the question

thats was kiddish question :P
THANKS ANNIE ;D
« Last Edit: January 21, 2011, 12:58:16 pm by SimoN »
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Offline Amii

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Re: IGCSE MATHS DOUBTS HERE !!!!
« Reply #119 on: January 21, 2011, 12:57:53 pm »
Quote from: SimoN on January 21, 2011, 12:54:26 pm
(x-3)^2 - 3^2 +10 would be:
(x-3)(x-3) - 9 + 10
x^2 -3x-3x +9 + 1
then:
x^2 -6x + 10

:o :o :o :o
i got it :D :D :D :D
1st factorize the question

thats was kiddish question :P
THANKS ANNIE ;D
No problem shona  :D
I will give you some "completing the square" method examples - Later

Now I gotta go take my bath  :D
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