Hey there! Sign in to join this conversationNew here? Join for free
 You are Here: Home >< Maths

Solutions of equations in general Watch

1. http://www.ocr.org.uk/Images/62241-q...hematics-3.pdf
For 8iii of the paper OCR FP3 paper above, in this examiners report: http://www.ocr.org.uk/Images/61726-e...ports-june.pdf
It says on page 26 that 'it was very worrying that 1 was oftenretained on the right hand side and statements' but I think this gives the correct answer so what's wrong?
2. What have you done?
3. (Original post by B_9710)
What have you done?
Sorry heres the mark scheme http://www.ocr.org.uk/Images/60318-m...ics-3-june.pdf
So basically for 8ii as can be seen in the mark scheme you begin with a factorised expression. Why can't you make that expression equal to ne like in the examiners report for 8iii( i would copy and paste but it becomes messed up). I say this becuase you end up with 2cos(squared theta)-1=1 form which you get that cos(theta)=1 or-1 which is the answer in the mark scheme
4. What you have is .
.So you get
, where .
Is this what you did?
5. What the examiner is trying to get at is that candidates tried to factorise without first ensuring that the RHS was zero. For the most part, when solving equations, factorising is only useful if the RHS is zero.

If candidates at FP3 do not realise that the RHS has to be zero when factorising is your solution strategy, this is worrying.

At GCSE/C1 you might often see ( foo )( bar )=1 >>> either foo = 1 or bar = 1 but if it happens at FP3 you wonder how?
6. (Original post by nerak99)
What the examiner is trying to get at is that candidates tried to factorise without first ensuring that the RHS was zero. For the most part, when solving equations, factorising is only useful if the RHS is zero.

If candidates at FP3 do not realise that the RHS has to be zero when factorising is your solution strategy, this is worrying.

At GCSE/C1 you might often see ( foo )( bar )=1 >>> either foo = 1 or bar = 1 but if it happens at FP3 you wonder how?
thanks for the reply. why does the right have to equal zero where factorising because 0 is just a number and you are trying where the graph crosses the line y=0 but if u can rearrange it in the another way the curve changes (but the equation is the same overall) you can find the solutions when y=c which is equivalent to finding when y=0 when you have the original equation? I hope it this clear
7. I think that the following is a gap in your understanding.

A multiplication sum with the result zero can only happen if one or more of the factors is zero. You use this fact to find the roots. Remember that factorise means 'make into a multiply' not 'make into brackets', although in polynomial factorisation this factorisation results in the form of brackets.

If a multiply happens to result in (say) 1, well you can nothing about the factors. They could be any one of an infinite set of multiplies that happend to result in 1 e.g. 0.000001 X 1000000 or 0.5 X 2 or -i X i ...
8. (Original post by nerak99)
I think that the following is a gap in your understanding.

A multiplication sum with the result zero can only happen if one or more of the factors is zero. You use this fact to find the roots. Remember that factorise means 'make into a multiply' not 'make into brackets', although in polynomial factorisation this factorisation results in the form of brackets.

If a multiply happens to result in (say) 1, well you can nothing about the factors. They could be any one of an infinite set of multiplies that happend to result in 1 e.g. 0.000001 X 1000000 or 0.5 X 2 or -i X i ...
thank you i get it know.

Reply
Submit reply
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: May 29, 2016
Today on TSR

Is this person a genius?

...with these A Level results?

I think I'm transgender AMA

Discussions on TSR

• Latest
• See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

Make your revision easier

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

How to use LaTex

Writing equations the easy way

Study habits of A* students

Top tips from students who have already aced their exams

Create your own Study Planner

Never miss a deadline again

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.