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# AS maths-coordinate geometry help! watch

1. Find in the form ax+by+c=0, where a, b and c are integers, the equation of the straight line which passes through each pair of points.
(2, -1.5) and (7,0)
I got 1.5x-5y-10.5=0
Am I correct?
2. not all your coefficients are integers tho'

3. (Original post by the bear)
not all your coefficients are integers tho'

Oh yeah
4. the gradient i got was 1.5/5, is that right???
5. ...
6. your formula is fine apart from the integer thing.
7. (Original post by Anonymous)
the gradient i got was 1.5/5, is that right???
Yes it is! Just multiply each term by the lowest common denominator to get the coefficients as integers.
8. (Original post by gcsemusicsucks)
Just multiply each term by the lowest common denominator to get the coefficients as integers.
that's what I did-
(y-0)=1.5/5(x-7) (*5)
5y=1.5x-10.5
=1.5x-5y-10.5=0
where have i gone wrong?
9. (Original post by Anonymous)
that's what I did-
(y-0)=1.5/5(x-7) (*5)
5y=1.5x-10.5
=1.5x-5y-10.5=0
where have i gone wrong?
since a, b and c are supposed to be integers, multiply the whole equation by 2 (the lowest common denominator)
10. (Original post by Caecilius_)
since a, b and c are supposed to be integers, multiply the whole equation by 2 (the lowest common denominator)
are you allowed to do that?
11. (Original post by Anonymous)
are you allowed to do that?
yes because if you multiply both sides of the equals sign by the same number there is no change in the equation of the line. If you do the same thing to both sides of any equation then the equation does not really change.
12. (Original post by Caecilius_)
yes because if you multiply both sides of the equals sign by the same number there is no change in the equation of the line. If you do the same thing to both sides of any equation then the equation does not really change.
do you have to x by 2 or can it be any number providing a, b and c are integers?
13. (Original post by Anonymous)
do you have to x by 2 or can it be any number providing a, b and c are integers?
any number providing they are integers, yes. However, it is best to give it as fully simplified as possible.
14. (Original post by Caecilius_)
any number providing they are integers, yes. However, it is best to give it as fully simplified as possible.
thx x

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