# Everyone doing maths read this!!!

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Thread starter 2 years ago
#1
for anyone struggling to remember the quadratic formulae you should know that you can write it on your calculator.

if you did not know you can input letters onto your calculator to do this press the alpha button and mess around with the top row of your calculator till you find the letters a, b and c. make a fraction symbol first then put the -b then the squared button then - 4ac on the bottom of the fraction press 2a. do this on your calculator just before the exam

as soon as you get in write it down on your question book
0
2 years ago
#2
smart
0
2 years ago
#3
(Original post by Akashv02)
for anyone struggling to remember the quadratic formulae you should know that you can write it on your calculator.

if you did not know you can input letters onto your calculator to do this press the alpha button and mess around with the top row of your calculator till you find the letters a, b and c. make a fraction symbol first then put the -b then the squared button then - 4ac on the bottom of the fraction press 2a. do this on your calculator just before the exam

as soon as you get in write it down on your question book
This is, strictly speaking, against the regulations, since you can't take in anything that has data stored on it, and so storing an equation on your calculator like this is not allowed. Your invigilator probably wouldn't notice though, but just be aware that if they did, you could be disqualified.

Also, you don't really need to memorise the quadratic formula, as it can be derived from completing the square.
4
2 years ago
#4
(Original post by Prasiortle)
This is, strictly speaking, against the regulations, since you can't take in anything that has data stored on it, and so storing an equation on your calculator like this is not allowed. Your invigilator probably wouldn't notice though, but just be aware that if they did, you could be disqualified.

Also, you don't really need to memorise the quadratic formula, as it can be derived from completing the square.
Yeah but in a fairly.short exam you don't have time to waste deriving it
1
2 years ago
#5
(Original post by Prasiortle)
This is, strictly speaking, against the regulations, since you can't take in anything that has data stored on it, and so storing an equation on your calculator like this is not allowed. Your invigilator probably wouldn't notice though, but just be aware that if they did, you could be disqualified.

Also, you don't really need to memorise the quadratic formula, as it can be derived from completing the square.
This guy knows. Never memorise a formula just derive it. π
0
2 years ago
#6
(Original post by (e^iΟ+1)^-1)
This guy knows. Never memorise a formula just derive it. π
I'm not saying "don't memorise". I'm simply saying that whenever you learn about a new result/theorem, it's always a good idea to understand the proof of it, so that you can have a mental model of mathematics as logically connected web, rather than a bunch of disjoint facts.
1
2 years ago
#7
(Original post by Prasiortle)
I'm not saying "don't memorise". I'm simply saying that whenever you learn about a new result/theorem, it's always a good idea to understand the proof of it, so that you can have a mental model of mathematics as logically connected web, rather than a bunch of disjoint facts.
a lot of proofs are too difficult for people to understand. I usually learn the proof and if the formula isn't in my memory I derive them.
0
2 years ago
#8
or get a casio classwiz, which can solve quadratics, cubics, and quartics. Also make an effort on non-calculator papers to remember/derive the formula (if it applies to you)
0
2 years ago
#9
(Original post by TheTroll73)
or get a casio classwiz, which can solve quadratics, cubics, and quartics. Also make an effort on non-calculator papers to remember/derive the formula (if it applies to you)
That's nothing. My TI-84 Plus CE-T can solve polynomial equations of up to degree 10.
0
2 years ago
#10
(Original post by Prasiortle)
That's nothing. My TI-84 Plus CE-T can solve polynomial equations of up to degree 10.
However the casio classwiz is way cheaper and really you should only use it for solving quadratics in the exam. If you solve cubics and up directly from the calculator, you may set yourself for a loss of marks for showing no working.

I do agree there may be some use in having a graphing calculator and school required us to have one at some point (not anymore). However, it definitely IS NOT a requirement and A* is more than achievable without.

Also my ti-nspire cx can solve up to degree 30 making 10 look like nothing in comparison, according to you .
0
2 years ago
#11
Guys, just memorize it. It's really not hard at all, and if you ever plan to do any maths beyond GCSE you'll need to recall it instantly.
1
2 years ago
#12
(Original post by TheTroll73)
However the casio classwiz is way cheaper and really you should only use it for solving quadratics in the exam. If you solve cubics and up directly from the calculator, you may set yourself for a loss of marks for showing no working.

I do agree there may be some use in having a graphing calculator and school required us to have one at some point (not anymore). However, it definitely IS NOT a requirement and A* is more than achievable without.

Also my ti-nspire cx can solve up to degree 30 making 10 look like nothing in comparison, according to you .
Firstly I'm long past A-Level (did it 7 years ago), and so I'm well aware of how these things are marked. In fact you're not quite right: if you write down the correct answer, and the question does not state "You must show your working" (or in the new spec, "You must show detailed reasoning" or "Do not use a calculator in this question"), you will get all the marks. I'm also well aware that the NSpire, and other calculators with a computer algebra system (e.g. Casio's ClassPad) can solve much higher-degree polynomial equations, but students cannot use such calculators in their exams as these ones have the ability to do symbolic algebra/calculus.

(Original post by DarthRoar)
Guys, just memorize it. It's really not hard at all, and if you ever plan to do any maths beyond GCSE you'll need to recall it instantly.
Yes, I memorised it in 2010, when I did GCSE. I also know how to derive it by completing the square. For cubic and higher equations, the "formulae" are far too complicated to memorise, but it is possible to memorise the procedure, e.g. for cubics you reduce to depressed form by the substitution x -> x - b/3a, then on the new cubic y^3 + Ay + B = 0, you solve s+t = A and 3st = -B, and the solution is y=s-t.
0
2 years ago
#13
(Original post by Prasiortle)
Firstly I'm long past A-Level (did it 7 years ago), and so I'm well aware of how these things are marked. In fact you're not quite right: if you write down the correct answer, and the question does not state "You must show your working" (or in the new spec, "You must show detailed reasoning" or "Do not use a calculator in this question", you will get all the marks. I'm also well aware that the NSpire, and other calculators with a computer algebra system (e.g. Casio's ClassPad) can solve much higher-degree polynomial equations, but students cannot use such calculators in their exams as these ones have the ability to do symbolic algebra/calculus.

Yes, I memorised it in 2010, when I did GCSE. I also know how to derive it by completing the square. For cubic and higher equations, the "formulae" are far too complicated to memorise, but it is possible to memorise the procedure, e.g. for cubics you reduce to depressed form by the substitution x -> x - b/3a, then on the new cubic y^3 + Ay + B = 0, you solve s+t = A and 3st = -B, and the solution is y=s-t.
the ti nspire cx has no computer algebra system. You may be confusing it with the ti nspire cx cas (cas stands for computer alegbra system).

And also, it may be that you did a level math with another exam board but for edexcel the front page for each paper says this: You should show sufficient working to make your methods clear. Answers without working may not gain full credit.
Therefore if one just write the answers that the calculator for said cubic then one misses out on marks.

I never have seen cubics (or higher order polynomials) in gcse math therefore I was only referring to A level and beyond
0
2 years ago
#14
Or you could press mode and pick option 5 (for equations) and then 3 (it has a quadratic equation form) and then insert your a,b, and, c values and it will give you the two solutions
0
2 years ago
#15
(Original post by TheTroll73)
the ti nspire cx has no computer algebra system. You may be confusing it with the ti nspire cx cas (cas stands for computer alegbra system).

And also, it may be that you did a level math with another exam board but for edexcel the front page for each paper says this: You should show sufficient working to make your methods clear. Answers without working may not gain full credit.
Therefore if one just write the answers that the calculator for said cubic then one misses out on marks.

I never have seen cubics (or higher order polynomials) in gcse math therefore I was only referring to A level and beyond
Yes, you're probably right about the TI-NSpire. Another similar example of a disallowed calculator is the TI-89 Titanium.

Edexcel say that on the front page because showing working is good practice, and I'm certainly not trying to encourage students to attempt to do everything in their head or on the calculator. But from Mr M at https://www.thestudentroom.co.uk/sho...php?t=2142680: "the right solution presented with no working will gain full credit in certain circumstances. If the question is a show or prove question then clearly you will get zero marks for just writing down the answer."
0
2 years ago
#16
(Original post by Prasiortle)
Yes, you're probably right about the TI-NSpire. Another similar example of a disallowed calculator is the TI-89 Titanium.

Edexcel say that on the front page because showing working is good practice, and I'm certainly not trying to encourage students to attempt to do everything in their head or on the calculator. But from Mr M at https://www.thestudentroom.co.uk/sho...php?t=2142680: "the right solution presented with no working will gain full credit in certain circumstances. If the question is a show or prove question then clearly you will get zero marks for just writing down the answer."
I think I get it now . It seems I misinterpreted "may" as "will".

I agree that it's pretty risky to not show working though (if you round wrong at the end for example the answer is 2.78 but you give 2.77 you still get 0 marks whereas with full working you'd lose only 1 mark for accuracy)
0
2 years ago
#17
(Original post by Akashv02)
for anyone struggling to remember the quadratic formulae you should know that you can write it on your calculator.

if you did not know you can input letters onto your calculator to do this press the alpha button and mess around with the top row of your calculator till you find the letters a, b and c. make a fraction symbol first then put the -b then the squared button then - 4ac on the bottom of the fraction press 2a. do this on your calculator just before the exam

as soon as you get in write it down on your question book
technically this is cheating
0
2 years ago
#18
(Original post by Prasiortle)
That's nothing. My TI-84 Plus CE-T can solve polynomial equations of up to degree 10.
how muxh it cost? might need myself one for my a level exams
0
2 years ago
#19
This post is going to be the beginning of invigilators examining kid's calculators before they enter the exam lol.
1
2 years ago
#20
(Original post by TheTroll73)
I think I get it now . It seems I misinterpreted "may" as "will".

I agree that it's pretty risky to not show working though (if you round wrong at the end for example the answer is 2.78 but you give 2.77 you still get 0 marks whereas with full working you'd lose only 1 mark for accuracy)
Yes, as I said, I'm not telling people not to show working. At A-Level there are a limited number of occasions where this would come up - e.g. solving polynomial equations, simultaneous equations, etc.,, and in the cases where the examiners specifically want to test whether the student can solve analytically, they will specify. E.g. in C1, being able to solve simultaneous equations where one is linear and one is quadratic is
a specific point on the syllabus, and so such questions invariably say "You must show your working". Similarly, Edexcel sometimes say "Solutions based solely on graphical or numerical methods will gain no credit." As for your last point, one would hope, at A-Level, that students can round their answers correctly.
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