core 1 maths help? Watch

Chelsea12345
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Find the equation of a line through the points A and B.
A is at (5,-1) and B is at (1,-2). Write your answer in the form of ax+by=c.

I got the answer x-y=6 but im not sure where i went wrong.
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PhoebeM99
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It's been a year since i've done core 1, so don't take what I say to be 100% fact.

But if you find the gradient by doing (y2-y1)/(x2-x1), you end up with -1/4.

Then you sub the gradient into y-y1=m(x-x1)
y-(-1)=-1/4(x-5)
4(y+1)=-1(x-5)
4y+4=-x+5
4y+x=1

So x+4y=1 is your answer.
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2859410
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(Original post by Chelsea12345)
Find the equation of a line through the points A and B.
A is at (5,-1) and B is at (1,-2). Write your answer in the form of ax+by=c.

I got the answer x-y=6 but im not sure where i went wrong.
what chapter is this in the c1 textbook?
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PhoebeM99
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(Original post by samantham999)
what chapter is this in the c1 textbook?
Co-ordinate geometry/ equation of a line
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Chelsea12345
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(Original post by samantham999)
what chapter is this in the c1 textbook?
the first one-"coordinates,points and lines"
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Notnek
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(Original post by PhoebeM99)
But if you find the gradient by doing (y2-y1)/(x2-x1), you end up with -1/4.
That's not right. And if you imagine the points you can see that the gradient should be positive.
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DylanJ42
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(Original post by PhoebeM99)
It's been a year since i've done core 1, so don't take what I say to be 100% fact.

But if you find the gradient by doing (y2-y1)/(x2-x1), you end up with -1/4.

Then you sub the gradient into y-y1=m(x-x1)
y-(-1)=-1/4(x-5)
4(y+1)=-1(x-5)
4y+4=-x+5
4y+x=1

So x+4y=1 is your answer.
gradient is 1/4, not -1/4.

(1,-2) doesnt lie on the line youve given
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Nuggetsarelife
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y= 1/4x - 9/4
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PhoebeM99
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(Original post by notnek)
That's not right. And if you imagine the points you can see that the gradient should be positive.
(Original post by DylanJ42)
gradient is 1/4, not -1/4.

(1,-2) doesnt lie on the line youve given
Whoops, I said it had been a while
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2859410
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(Original post by Chelsea12345)
the first one-"coordinates,points and lines"
ocr? or edexcel
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Chelsea12345
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(Original post by samantham999)
ocr? or edexcel
ocr
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Luke7456
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y1-y2= -1-(-2)=1 x1-x2 =5-1=4 so gradient is 1/4

y-y1=M(x-x1)

y-(-1)=1/4(x-5)

y+1=1/4X-5/4
4y+4=x-5
4y=x-9
0=x-4y-9
x-4y=9
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TheConfusedMedic
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find out the gradient by using the two points given.
Then sub in the coordinates of one of the points and the gradient into (y-y1)/(x-x1) = m, rearrange and you get your equation.
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Chittesh14
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(Original post by surina16)
find out the gradient by using the two points given.
Then sub in the coordinates of one of the points and the gradient into (y-y1)/(x-x1) = m, rearrange and you get your equation.
Why not just simply sub it into y - y1 = m(x-x1) ?
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TheConfusedMedic
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(Original post by Chittesh14)
Why not just simply sub it into y - y1 = m(x-x1) ?
Its the same thing? Idk, our teacher told us to use our one just because all you have to do then is cross multiply Both ways are the same tbh :lol:
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Chittesh14
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(Original post by surina16)
Its the same thing? Idk, our teacher told us to use our one just because all you have to do then is cross multiply Both ways are the same tbh :lol:
Yeah ik... I was being sarcastic lmao. Depends on what you're told lol same formula so doesn't matter!
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