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

1. (Original post by Alexion)
Unfortunately, the exam boards don't accept this genius method of working as valid
You need working to write down the equation of a straight line?! C'mon. Should I split every summation question into me adding 1 + 1 + 1 + 1 + 1 + ... + 1 over again to show my working?
2. (Original post by Student403)
I can think of one exception to that

Solving quadratics
Ah, but that's just factorising that counts as a valid step
3. Let's face it. Most people who do A-level maths don't actually understand maths. They have just picked it as an A-level that will look good in the future.
4. (Original post by Alexion)
Ah, but that's just factorising that counts as a valid step
Oh I meant jumping from

12x^2 + 5x - 2 = 0

To x = -2/3, x = 1/4

Although maybe this is because it's done on a calculator.. Idk
5. (Original post by Student403)
#JustMechanicsThings

"A particle is accelerated at 5ms^-2 from rest. How long does it take to travel 100m? [7 Marks]"
(40)^1/2
6. (Original post by Alexion)
Unfortunately, the exam boards don't accept this genius method of working as valid

My point is that it's so simple it can be done in your head.

I'm fine with either method really. It's the forcing of students to learn the "A Level method" that I have an issue with.
7. (Original post by ememoville)
(40)^1/2
8. I like the second method more. I think actually being able to calculate something means I have more confidence in my answer, whereas if I just wrote down the equation I'd feel like I'd be more likely to make a mistake.
9. (Original post by Student403)
Oh I meant jumping from

12x^2 + 5x - 2 = 0

To x = -2/3, x = 1/4
blasphemy...

(Original post by notnek)

My point is that it's so simple it can be done in your head.

I'm fine with either method really. It's the forcing of students to learn the "A Level method" that I have an issue with.
TBH yeah, it's true - but I guess what you're really doing by working it through in your head is just the "A-level method" with a couple steps shaved off.

Plus if the points you get given are a long way from the axes then it becomes a little more necessary to use a formula idk
10. (Original post by Zacken)
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.
Just remembered there is, I guess, technically some in S1...
11. Always use y=mx+c personally, and I don't understand why my classmates all use that other equation (that I have never even memorised). It just seems so simpler, I can't think of any reason to use the other one if they both lead to the same answer.
12. (Original post by Slowbro93)
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
I'd argue that you have it the other way around. The y=mx+c is just reading out of a book. The other one teaches you why concepts work. (y1 -y2) =m (x1-x2) is much better in terms of learning but i never use it in exams because it's longer.
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)

I'm already bored.

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
The teacher could've crossed it out because of the student loosing M1 marks and etc

However you have to remember that maths is taken by students with a whole range of mathematical abilities and the exam board has to be able to cater to both D grade and A grade candidates. Working it out that way may be easier for people with a lack of understand of the concept or poor mental maths
14. (Original post by RonnieRJ)
The teacher could've crossed it out because of the student loosing M1 marks and etc
Any method to find the equation is allowed in exams.
15. (Original post by notnek)
Any method to find the equation is allowed in exams.
Well that's fine, it was a suggestion as someone previously mentioned It wasn't accepted as valid?
16. (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)

I'm already bored.

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 prefer y = mx + c as it makes you think about what you are doing.

Once you know the gradient you have a 'family' of lines then the specific point choose which one of them it is ie which translation of y = mx you want.

I don't make my students use either method - as long as they use it correctly and explain clearly it's fine with me.
17. perfect !
18. Oh. I use whatever method I prefer on the day. I think neither method is "better" or less boring.

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