Year 13 Maths Help Thread

Announcements Posted on
How helpful is our apprenticeship zone? Have your say with our short survey 02-12-2016
    Online

    3
    ReputationRep:
    (Original post by kiiten)
    (x+1)^3 6 (x+2)^5 + (x+2)^6 3(x+1)^2

    But thats not in the form (x+1)^2 (x+2)^5 (ax + b) D:
    No offence intended, I think you are giving up too quickly or being too quick to ask questions. Alternatively, you've hit a mental block, which is also fine, happens to the best of us. Spending too long on one problem can be frustrating and draining but equally a good learning experience.

    Have a think about what you have just asked and how you can answer it for yourself
    Online

    2
    ReputationRep:
    (Original post by SeanFM)
    No offence intended, I think you are giving up too quickly or being too quick to ask questions. Alternatively, you've hit a mental block, which is also fine, happens to the best of us. Spending too long on one problem can be frustrating and draining but equally a good learning experience.

    Have a think about what you have just asked and how you can answer it for yourself
    Maybe but i cant see it, I only see 2 terms that are almost in the correct form. Im out of ideas with this question , I dont know what to do anymore :argh:
    Online

    3
    ReputationRep:
    (Original post by kiiten)
    Maybe but i cant see it, I only see 2 terms that are almost in the correct form. Im out of ideas with this question , I dont know what to do anymore :argh:
    Your answer in your previous post is correct, you are actually required to make it look like that form.

    Here's some advice for you then, call (x+2) = a, (x+1) = b and rewrite everything in terms of a and b, from your 'almost correct form' stage and including the final form. Then see if it hits you (though maybe c and d are better to use since a and b are in the final form)
    Online

    2
    ReputationRep:
    (Original post by SeanFM)
    Your answer in your previous post is correct, you are actually required to make it look like that form.

    Here's some advice for you then, call (x+2) = a, (x+1) = b and rewrite everything in terms of a and b, from your 'almost correct form' stage and including the final form. Then see if it hits you (though maybe c and d are better to use since a and b are in the final form)
    9x + 12 ??

    I still feel like this is wrong and if i had a similar question i wouldnt know how to get it into the correct form. I understood what you said but it 'didnt hit me' (i wouldnt have thought og answering it like this)
    Online

    3
    ReputationRep:
    (Original post by kiiten)
    9x + 12 ??

    I still feel like this is wrong and if i had a similar question i wouldnt know how to get it into the correct form. I understood what you said but it 'didnt hit me' (i wouldnt have thought og answering it like this)
    I'm not sure what your 9x+12 is referring to, the ax + b? I haven't done this myself so I don't know what the answer is.
    (x+1)^3 6 (x+2)^5 + (x+2)^6 3(x+1)^2

    But thats not in the form (x+1)^2 (x+2)^5 (ax + b) D:
    given c = (x+2), d = (x+1), the differentiated output is  6d^3c^5 + 3c^6d^2 and the required form is d^2c^5(ax+b)... how have the two terms been turned into one?
    Online

    2
    ReputationRep:
    (Original post by SeanFM)
    I'm not sure what your 9x+12 is referring to, the ax + b? I haven't done this myself so I don't know what the answer is.

    given c = (x+2), d = (x+1), the differentiated output is  6d^3c^5 + 3c^6d^2 and the required form is d^2c^5(ax+b)... how have the two terms been turned into one?
    Oh yeah, sorry i mean is ax + b = 9x + 12.

    Yeah thats what i did - kinda....Name:  Screenshot 2016-10-05 19.21.53.png
Views: 25
Size:  23.3 KB
    Online

    3
    ReputationRep:
    (Original post by kiiten)
    Oh yeah, sorry i mean is ax + b = 9x + 12.

    Yeah thats what i did - kinda....Name:  Screenshot 2016-10-05 19.21.53.png
Views: 25
Size:  23.3 KB
    Looks right to me does it look right to you?
    Online

    2
    ReputationRep:
    (Original post by SeanFM)
    Looks right to me does it look right to you?
    Yes? Yayyy finally im so glad i finally answered this question now. Thanks for your help - and sorry if i was annoying.
    Online

    3
    ReputationRep:
    (Original post by kiiten)
    Yes? Yayyy finally im so glad i finally answered this question now. Thanks for your help - and sorry if i was annoying.
    When you are stuck it is important to look at the definitions and similar examples, then think about what topics the question is testing you on, and if a form is given, how you can get to it (rather than looking at it and wondering why your answer isn't in the correct form when you think you have done everything right)
    Offline

    3
    ReputationRep:
    Right so the question is to express:

    f(x)=(2x+3)/(x-1) as f(x)=a + b/(x-1)

    Was I right to do this...

    (2x+3)/(x-1)=a + b/(x-1)

    (2x+3)=a(x-1) + b

    sub x=1

    5=b

    sub b=5 and then end up a=2

    so f(x) = 2 +5/(x-1)

    Was this the correct method? I just used the partial fractions method, but this question is for C3, although it did work.
    Offline

    3
    ReputationRep:
    (Original post by jamestg)
    Right so the question is to express:

    f(x)=(2x+3)/(x-1) as f(x)=a + b/(x-1)

    Was I right to do this...

    (2x+3)/(x-1)=a + b/(x-1)

    (2x+3)=a(x-1) + b

    sub x=1

    5=b

    sub b=5 and then end up a=2

    so f(x) = 2 +5/(x-1)

    Was this the correct method? I just used the partial fractions method, but this question is for C3, although it did work.
    It's correct. But it may be easier to realise that  \displaystyle \frac{2x+3}{x-1} \equiv \frac{2(x-1)+5}{x-1} and split the fraction up.
    You can also just do it using algebraic division as you normally would
    Offline

    3
    ReputationRep:
    (Original post by B_9710)
    It's correct. But it may be easier to realise that  \displaystyle \frac{2x+3}{x-1} \equiv \frac{2(x-1)+5}{x-1} and split the fraction up.
    You can also just do it using algebraic division as you normally would
    Damn, algebraic division would have been much easier...

    At least I now know this before the exam

    Thanks for your help!
    • Thread Starter
    Offline

    2
    ReputationRep:
    Hi, are there any relatively easy STEP I papers from recent years? I was told that 2007 was relatively easy but I could only manage 4 questions out of that paper.
    Offline

    3
    ReputationRep:
    (Original post by Palette)
    Hi, are there any relatively easy STEP I papers from recent years? I was told that 2007 was relatively easy but I could only manage 4 questions out of that paper.
    2010
    Offline

    3
    ReputationRep:
    Can someone help me with implicit differentiation?

    Find the gradient of 3y=\frac{8x^2}{4x^2-3y^3} at the point (3,2)

    I got the answer to be \frac{4}{9} but it's wrong.
    Offline

    3
    ReputationRep:
    Name:  image.jpg
Views: 21
Size:  500.1 KB

    Working out maybe helpful
    Offline

    2
    ReputationRep:
    (Original post by jamestg)
    Can someone help me with implicit differentiation?

    Find the gradient of 3y=\frac{8x^2}{4x^2-3y^3} at the point (3,2)

    I got the answer to be \frac{4}{9} but it's wrong.
    Multiply both sides by the denom

    12x^2y-9y^4=8x^2
    differentiate with respect to x
    24xy+12x^2(dy/dx)-36y^3(dy/dx)=16x
    (dy/dx)(12x^2-36y^3)=16x-24xy
    put in the numbers
    (dy/dx)(108-288)=48-144
    dy/dx=-96/-180=16/30=8/15
    Offline

    3
    ReputationRep:
    Whoops realised when I did the quotient rule I didn't divide by v^{2}
    Offline

    3
    ReputationRep:
    (Original post by MathMoFarah)
    Multiply both sides by the denom

    12x^2y-9y^4=8x^2
    differentiate with respect to x
    24xy+12x^2(dy/dx)-36y^3(dy/dx)=16x
    (dy/dx)(12x^2-36y^3)=16x-24xy
    put in the numbers
    (dy/dx)(108-288)=48-144
    dy/dx=-96/-180=16/30=8/15
    Damn I even considered doing it that way initially

    Thanks for the help!
    Offline

    2
    ReputationRep:
    Q1.7
    How many zeros are there at the end of the number 100! ?
    I don't get what that exclamation mark means, and 2 isn't the answer. I remember using it as symbol in AS maths but not anything else.

    Q1.11
    A salesmen drives from L to B. The first half of the distance he drives at a constant speed of 80 mph. The second half he drives at a constant speed of 120 mph. What is his average speed for the total journey?

    I don't understand why the answer is 96 mph and not 100?
 
 
 
Write a reply… Reply
Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: November 26, 2016
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.

Today on TSR
Poll
Would you rather have...?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read here first

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

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
Study resources

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

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