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GCSE - Arithmetic Sequence watch

1. (Original post by Y11_Maths)
I didn’t say it doesn’t work I’m saying it is incorrect as you would not obtain any marks from it since that is not how the question is meant to be answered.
unless the question specifies a particular method then the examiners will accept any valid approach
2. (Original post by the bear)
unless the question specifies a particular method then the examiners will accept any valid approach
In this case the only valid approach is solving for x so...
3. (Original post by Y11_Maths)
In this case the only valid approach is solving for x so...
the other method is also valid.
4. (Original post by the bear)
the other method is also valid.
It doesn’t work though...
5. (Original post by Y11_Maths)
It doesn’t work though...
apart from it does
6. psc---maths
7. I didn't- I merely said that the argument the op used didn't work due to their phrasing- they could rephrase it and it would work. (Although I must admit I think finding the possible value of x is the easiest way!)
8. (Original post by the bear)
the other method is also valid.
Can't you "prove" that is not a term in the sequence (despite it being defined as such) with your method?

. Well now clearly isn't a factor of the RHS so isn't in the sequence. The point has already been made by another poster "psc" - we need to check if there is cancellation for the value of x which makes the given terms an arithmetic sequence, not all x. The fact that Y11_Maths was just initially responding with "you wouldn't get the marks as it's a different method" probably caused further confusion.
9. (Original post by I hate maths)
Can't you "prove" that is not a term in the sequence (despite it being defined as such) with your method?

. Well now clearly isn't a factor of the RHS so isn't in the sequence. The point has already been made by another poster "psc" - we need to check if there is cancellation for the value of x which makes the given terms an arithmetic sequence, not all x. The fact that Y11_Maths was just initially responding with "you wouldn't get the marks as it's a different method" probably caused further confusion.
yes you are quite right.
10. (Original post by Y11_Maths)
I didn’t say it doesn’t work I’m saying it is incorrect as you would not obtain any marks from it since that is not how the question is meant to be answered.
There's no such thing as "how a question is meant to be answered" in a maths exam question. If your approach is valid then you will get the marks.

Although there will be some approaches that are nicer/faster than others. If you meant this then you weren't explaining yourself clearly.
11. (Original post by Notnek)
There's no such thing as "how a question is meant to be answered" in a maths exam question. If your approach is valid then you will get the marks.

Although there will be some approaches that are nicer/faster than others. If you meant this then you weren't explaining yourself clearly.
This is especially true in any hard Maths problem (and the Olympiads). Which is what makes Maths the best subject (definitely not biased :P)
12. (Original post by the bear)
yes you are quite right.
Your method is much more sophisticated than mine and is probably why you didn’t think this was GCSE in the first place. The easiest way to do it is solve for x which I’m pretty sure is the way the question wants you to (I haven’t bought the answers but even my teacher said this was the way to do it). I don’t think your method would gain full marks though as it just seems to obscure from the problem if you get me? The question states at the beginning it is an arithmetic sequence which means that any 2 terms subtracted will equal another 2 terms subtracted from each other. Set these equal to each other and you can form a quadratic to solve for x. The rest is substitution
13. (Original post by Y11_Maths)
Your method is much more sophisticated than mine and is probably why you didn’t think this was GCSE in the first place. The easiest way to do it is solve for x which I’m pretty sure is the way the question wants you to (I haven’t bought the answers but even my teacher said this was the way to do it). I don’t think your method would gain full marks though as it just seems to obscure from the problem if you get me? The question states at the beginning it is an arithmetic sequence which means that any 2 terms subtracted will equal another 2 terms subtracted from each other. Set these equal to each other and you can form a quadratic to solve for x. The rest is substitution
That's true but I suppose what you mean is that is the "expected" solution students may write up but some students get creative with Maths problems (his answer) which I'd always recommend since it makes you become able to answer complicated Maths questions that aren't always obvious.
14. (Original post by thekidwhogames)
That's true but I suppose what you mean is that is the "expected" solution students may write up but some students get creative with Maths problems (his answer) which I'd always recommend since it makes you become able to answer complicated Maths questions that aren't always obvious.
I guess that is where I lack in my mathematical abilities. Props to the bear for being more openly minded towards this question. My bad fellas :/
15. (Original post by Y11_Maths)
Your method is much more sophisticated than mine and is probably why you didn’t think this was GCSE in the first place. The easiest way to do it is solve for x which I’m pretty sure is the way the question wants you to (I haven’t bought the answers but even my teacher said this was the way to do it). I don’t think your method would gain full marks though as it just seems to obscure from the problem if you get me? The question states at the beginning it is an arithmetic sequence which means that any 2 terms subtracted will equal another 2 terms subtracted from each other. Set these equal to each other and you can form a quadratic to solve for x. The rest is substitution
From this I can tell you're missing the point. Bear's method may be more technical than a correct solution (remember, it's incorrect and I think you're unaware of this still), but any examiner worth their salt should be able to follow it. And if it was correct, it would deserve full marks. You're thinking of maths as a subject where you bring out the correct learned technique, for the correct situation or topic, in the correct paper, at the correct time, to score the correct amount of points.

EDIT: Well that was bad timing.
16. (Original post by I hate maths)
From this I can tell you're missing the point. Bear's method may be more technical than a correct solution (remember, it's incorrect and I think you're unaware of this still), but any examiner worth their salt should be able to follow it. And if it was correct, it would deserve full marks. You're thinking of maths as a subject where you bring out the correct learned technique, for the correct situation or topic, in the correct paper, at the correct time, to score the correct amount of points.
Sincere apologies
17. (Original post by Y11_Maths)
I guess that is where I lack in my mathematical abilities. Props to the bear for being more openly minded towards this question. My bad fellas :/
let us not forget irrelevant kid who contributed this interesting problem & ihatemaths and psc---maths who helped.

Well played Sirs !
18. (Original post by Y11_Maths)
Sincere apologies
You don't have to apologies - it's just a learning point that everybody (including myself and people on this thread) go through.
19. (Original post by thekidwhogames)
You don't have to apologies - it's just a learning point that everybody (including myself and people on this thread) go through.

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