I need some help desperately with my maths!!! Watch

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CHAD
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#1
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Hi
Can anyone explain to me how to solve a simualtaneous equation? I need to know for my mock maths gcse tomorrow.
Thank-you!
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_EMMA_
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(Original post by CHAD)
Hi
Can anyone explain to me how to solve a simualtaneous equation? I need to know for my mock maths gcse tomorrow.
Thank-you!
do you have an example?
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CHAD
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(Original post by _EMMA_)
do you have an example?

yeah:


x2 - 4y2 = 24
x + 2y = 6
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George-W-Duck
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ive replied on the other identical thread youve posted.
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JSM
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repeating youself is not conduicive to recieving help. and i would help if i could but im rubbish at maths and hate it.
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4Ed
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(Original post by CHAD)
yeah:


x2 - 4y2 = 24
x + 2y = 6
do you mean x squared (x^2) when you say x2 and y2?
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CHAD
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(Original post by 4Ed)
do you mean x squared (x^2) when you say x2 and y2?

yeah sorry, didnt know how 2 rite it
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4Ed
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(Original post by CHAD)
yeah:


x2 - 4y2 = 24
x + 2y = 6

ok well taking the second equation you have x = 6 - 2y

therefore

x^2 = 36 - 24y + 4y^2

sub that into the first equation and you get:

36 - 24 y + 4y^2 - 4y^2 = 24

Thus 24 y = 12 and y = 1/2. and x = 5.
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Nima
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(Original post by _EMMA_)
do you have an example?
6x + 2y = 10 (A)
3x + 4y = 20 (B)

Multiply (B) by 2 in order to get mathcing co-efficeints of x for both (A) and (B) :

6x + 2y = 10
6x + 8y = 40

subtract (B) from (A) in order to clear x's:

-6y = - 30
6y = 30
y = 5

Sub. y = 5 back into (A) in order to find the value of x:

6x + (2 * 5) = 10
6x + 10 = 10
6x = 0
x = 0

y = 5 and x = 0 are the 2 solutions for the simultaneous equations (A) and (B).
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Harry Potter
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Rearrange one of the equations to make x or y the subject:

x + 2y = 6

x = 6-2y

Now we know that x is the same as 6-2y so in the other equation we can substitute x for 6-2y:

x2 - 4y2 = 24

(6 - 2y)2 - 4y2 = 24

now multiply out the brackets and rearrange a bit:

36 - 24y + 4y2 -4y2 =24

24y = 36 -24 = 12

y = 12/24 = 1/2

now we can substitue 1/2 for y in one of the original equations:

x + 2*1/2 = 6

x = 6-1 = 5
Harry Potter
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(Original post by bono)

y = 5 and x = 0 are the 2 solutions for the simultaneous equations (A) and (B).
lol damn. I've probably made a silly mistake.

EDIT: different question :rolleyes:
4Ed
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(Original post by Harry Potter)
lol damn. I've probably made a silly mistake.
don't worry i got the same as you (see above).

besides bono was referring to his own simultaneous equation example.
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Nima
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(Original post by 4Ed)
don't worry i got the same as you (see above).

besides bono was referring to his own simultaneous equation example.
i made up my own example guys.........
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Nima
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(Original post by 4Ed)
don't worry i got the same as you (see above).

besides bono was referring to his own simultaneous equation example.
i presumed at gcse it would be simpler simultaneous equations like this, as u dont get anything ahrder than this realy at gcse.
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4Ed
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(Original post by bono)
i presumed at gcse it would be simpler simultaneous equations like this, as u dont get anything ahrder than this realy at gcse.
his involved squares! although they did cancel out in the end..... there was probably a way to do it without the squaring, dunno.....
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CHAD
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#16
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nah, i dont find em easy, but my strength isnt exactly maths. neawy thanks for the help everyone!
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CHAD
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#17
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Hi
Sorry to ask again. I know this is gonna sound dumb but could you explain again, cos I dont understand where you get the 36 from. Also the answers are
x = 5
y = 0.5

I just don't know how to get there.
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GH
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#18
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(Original post by CHAD)
Hi
Sorry to ask again. I know this is gonna sound dumb but could you explain again, cos I dont understand where you get the 36 from. Also the answers are
x = 5
y = 0.5

I just don't know how to get there.
When you subsitute x= 6- 2y into the irst equation.

i.e. x^2

therefore (6-2y)(6-2y) = 36 - 24y + 4y^2

and just use y=0.5 from the answer that you get, put it into first equation to get the x answer.
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4Ed
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(Original post by CHAD)
Hi
Sorry to ask again. I know this is gonna sound dumb but could you explain again, cos I dont understand where you get the 36 from. Also the answers are
x = 5
y = 0.5

I just don't know how to get there.
do you know how to multiply out (6 - 2y) squared?

that is equal to x from the 2nd equation, and gives you your 36.
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_EMMA_
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(Original post by CHAD)
Hi
Sorry to ask again. I know this is gonna sound dumb but could you explain again, cos I dont understand where you get the 36 from. Also the answers are
x = 5
y = 0.5

I just don't know how to get there.
that is the answers 4ED wrote

look at this from HarryPotter:
x2 - 4y2 = 24

(6 - 2y)2 - 4y2 = 24

now multiply out the brackets and rearrange a bit:

36 - 24y + 4y2 -4y2 =24

24y = 36 -24 = 12

y = 12/24 = 1/2


( ) this means that you have to multiply everything in it with what is outside that's where 36 came from
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