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# Year 13 Maths Help Thread

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Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
1. (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
2. (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
3. (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
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)
4. (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)
5. (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 and the required form is ... how have the two terms been turned into one?
6. (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 and the required form is ... 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....
7. (Original post by kiiten)
Oh yeah, sorry i mean is ax + b = 9x + 12.

Yeah thats what i did - kinda....
Looks right to me does it look right to you?
8. (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.
9. (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)
10. 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.
11. (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 and split the fraction up.
You can also just do it using algebraic division as you normally would
12. (Original post by B_9710)
It's correct. But it may be easier to realise that 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

13. 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.
14. (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
15. Can someone help me with implicit differentiation?

Find the gradient of at the point (3,2)

I got the answer to be but it's wrong.

17. (Original post by jamestg)
Can someone help me with implicit differentiation?

Find the gradient of at the point (3,2)

I got the answer to be 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
18. Whoops realised when I did the quotient rule I didn't divide by
19. (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!
20. 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?

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