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# y = mx + c vs y - y1=m(x - x1) watch

1. FInd the equation of the straight line with gradient 3 which passes through (2, 10).

y = mx + c :

In my head I can see that the eqn is y = 3x + c and c must be 4 for the point to be satisfied. With practice, this can be done in less than a second in your head.

(I realise there are examples that are harder than this but they're not as good for my argument!)

Now

y - y1 = m(x - x1) :

y - 10 = 3(x - 2)

Why are A Level students forced to use y - y1 = m(x - x1)? One of my tutees the other day had crosses all over their work because they didn't use the "A Level method" in their working.

Please can someone explain the benefits of using the "A Level method" ? I'm prepared to back down if someone can convince me
2. I think it's just easier to use the 2nd form.
You don't have to work anything out, all you have to do is plug the numbers in.
3. (Original post by notnek)
Please can someone explain the benefits of using the "A Level method" ? I'm prepared to back down if someone can convince me
I used to have a preference for myself and never really bothered learning the alternate formula, I have since then come to learn it and remove any particular preference for one form, I use whichever is most convenient at the time. In your first example, I'd used , if a question gave me two ugly points and I found a rational (non-integer) gradient and the question asked me to write my equation in the form , I'd use the alternate method.

On the other hand, whilst I'm nowhere near an education specialist such as yourself, here's some food for though.

Argument for.
Argument against.
4. (Original post by B_9710)
I think it's just easier to use the 2nd form.
You don't have to work anything out, all you have to do is plug the numbers in.
You have to plug numbers in with both methods.
5. Just speculation. I'm really not sure

Maybe because if they allowed the first, too many students would feel a bit too confident try to use it and make silly mistakes? It seems quite an easy method to slip up with if you don't easily think in that way.
6. (Original post by notnek)
You have to plug numbers in with both methods.
If say you work out the equation of the tangent at a point and then you need to work out the equation of the normal at the same point all you do when using the second version is using the negative reciprocal gradient and your done. No messing about.
7. (Original post by notnek)
FInd the equation of the straight line with gradient 3 which passes through (2, 10).

y = mx + c :

In my head I can see that the eqn is y = 3x + c and c must be 4 for the point to be satisfied. With practice, this can be done in less than a second in your head.

(I realise there are examples that are harder than this but they're not as good for my argument!)

Now

y - y1 = m(x - x1) :

y - 10 = 3(x - 2)

Why are A Level students forced to use y - y1 = m(x - x1)? One of my tutees the other day had crosses all over their work because they didn't use the "A Level method" in their working.

Please can someone explain the benefits of using the "A Level method" ? I'm prepared to back down if someone can convince me
I don't think students are forced to learn the second one. I always the first one was just GCSE knowledge.
8. More marks to distribute in the exam?
9. (Original post by B_9710)
If say you work out the equation of the tangent at a point and then you need to work out the equation of the normal at the same point all you do when using the second version is using the negative reciprocal gradient and your done. No messing about.
That's the same for the other method too, though... You just need to use the negative reciprocal gradient and you're done.
10. (Original post by B_9710)
I don't think students are forced to learn the second one. I always the first one was just GCSE knowledge.
From my experience students are often forced to use it.

One reason is that the main textbook used for Edexcel has a whole exercise where the y - y1=m(x-x1) formula is taught.
11. (Original post by Zacken)
I used to have a preference for myself and never really bothered learning the alternate formula, I have since then come to learn it and remove any particular preference for one form, I use whichever is most convenient at the time. In your first example, I'd used , if a question gave me two ugly points and I found a rational (non-integer) gradient and the question asked me to write my equation in the form , I'd use the alternate method.

On the other hand, whilst I'm nowhere near an education specialist such as yourself, here's some food for though.

Argument for.
Argument against.
I say get rid of and (stupid format) and keep straight line graphs a GCSE topic.

It will free up room for other topics. How about some set theory
12. (Original post by notnek)
I say get rid of and (stupid format) and keep straight line graphs a GCSE topic.

It will free up room for other topics. How about some set theory
I wouldn't be entirely adverse to that idea.

It boggles me that there isn't any set theory in GCSE, my CIE IGCSE certainly had an ample amount.
13. (Original post by notnek)
FInd the equation of the straight line with gradient 3 which passes through (2, 10).

y = mx + c :

In my head I can see that the eqn is y = 3x + c and c must be 4 for the point to be satisfied. With practice, this can be done in less than a second in your head.

(I realise there are examples that are harder than this but they're not as good for my argument!)

Now

y - y1 = m(x - x1) :

y - 10 = 3(x - 2)

Why are A Level students forced to use y - y1 = m(x - x1)? One of my tutees the other day had crosses all over their work because they didn't use the "A Level method" in their working.

Please can someone explain the benefits of using the "A Level method" ? I'm prepared to back down if someone can convince me
Right, excuse if I don't make sense as I've had almost a bottle of wine

My view on it is that you have two types of teachers. The ones who actually understand why particular concepts work and thus you can use the method, and the other who essentially is "everything as to be done by the book, any deviation from that and you're wrong". I don't think it's the case that the teachers are saying that it's wrong, but when you have something drummed into your minds in terms of formulae and you don't understand it, any form of alternative is seen as wrong in every way shape and form. I was penalised by this way of thinking by two of my three maths teachers during AS but this wasn't the case for the third.

If it's the case that they ever give you the gradient within the question, I can sort of see the reasoning to the different method. But even that still wouldn't convince me. I never bothered learning it because I saw it as unnecessary formula to remember

/ramble
14. (Original post by SeanFM)
More marks to distribute in the exam?
#JustMechanicsThings

"A particle is accelerated at 5ms^-2 from rest. How long does it take to travel 100m? [7 Marks]"
15. (Original post by Zacken)
I wouldn't be entirely adverse to that idea.

It boggles me that there isn't any set theory in GCSE, my CIE IGCSE certainly had an ample amount.
It's in the new GCSE - about time.
16. (Original post by Zacken)
I wouldn't be entirely adverse to that idea.

It boggles me that there isn't any set theory in GCSE, my CIE IGCSE certainly had an ample amount.
Set theory at GCSE ? I didn't study set theory formally until university
17. (Original post by 13 1 20 8 42)
Set theory at GCSE ? I didn't study set theory formally until university
It was only about the first few pages of a set theory book. Learning about the operations: unions, intersections, complements and their connections with Venn diagrams and doing some algebra with them plus some other stuff I don't quite remember.
18. excellent ...
all we need in here is Mutley
19. (Original post by notnek)
In my head I can see
Unfortunately, the exam boards don't accept this genius method of working as valid
20. (Original post by Alexion)
Unfortunately, the exam boards don't accept this genius method of working as valid
I can think of one exception to that

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