# core 1 maths help?Watch

#1
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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2 years ago
#2
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

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2 years ago
#3
(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?
2 years ago
#4
(Original post by samantham999)
what chapter is this in the c1 textbook?
Co-ordinate geometry/ equation of a line
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#5
(Original post by samantham999)
what chapter is this in the c1 textbook?
the first one-"coordinates,points and lines"
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2 years ago
#6
(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.
0
2 years ago
#7
(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

(1,-2) doesnt lie on the line youve given
0
2 years ago
#8
y= 1/4x - 9/4
0
2 years ago
#9
(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)

(1,-2) doesnt lie on the line youve given
Whoops, I said it had been a while
1
2 years ago
#10
(Original post by Chelsea12345)
the first one-"coordinates,points and lines"
ocr? or edexcel
#11
(Original post by samantham999)
ocr? or edexcel
ocr
0
2 years ago
#12
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
0
2 years ago
#13
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.
0
2 years ago
#14
(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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2 years ago
#15
(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
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2 years ago
#16
(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
Yeah ik... I was being sarcastic lmao. Depends on what you're told lol same formula so doesn't matter!
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