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C2 Maths AS aqa 2016 (unofficial mark scheme new)

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Original post by Dapperblook22
There is another way to prove the stretch by rearranging the first equation given. See attached working, I went through this with a friend after the exam :smile:


That's over complicated I would say, have a look at what I replied before.
what would be 90 ums?????
Original post by wil_is_he
That's over complicated I would say, have a look at what I replied before.


I thought it would be the most intuitive, as this just needs rearranging. Each to their own methods however :tongue:
Original post by Myachii
Allow me to explain myself:
You could do the sum of the first three numbers using the formula (which is what I presume you used), or you could just figure them out (26, 24, 22) because it was an arithmetic series so subtracting two wasn't that hard :P

I said it was like using a sledgehammer to crack a nut because if you used the formula to calculate the sum of the first three, you made yourself a hell of a lot more work and more room for error.


Yeah I didn't clock about the first and second terms so I used the sum formula. Think I got it right though so it's calm :smile:
Original post by beanigger


3)a) differentiate something to get 3x-1/2 -1 [2]
b) find y co-ordinate of the maximum point M M(9,6) [3]
c) equation of normal to curve at P i think P was (5,6) y=-2x+13 [2]
d) the normal to curve at P is translated by (0,k) find value of k, k = 5.5 [3]



I beleive part d), the vector was (k,0), and the answer (the one I got atleast) was -5.5
Original post by Rowan396
I beleive part d), the vector was (k,0), and the answer (the one I got atleast) was -5.5


Same!
Stretch question:

x2+9\sqrt{x^2+9} to 3x2+13\sqrt{x^2+1}

Notice 3x2+1=9x2+1=9(x2+1)=9x2+9=(3x)2+93\sqrt{x^2+1} = \sqrt{9} \sqrt{x^2+1} = \sqrt{9(x^2+1)} = \sqrt{9x^2+9} = \sqrt{(3x)^2+9}

So it's a stretch in the x-direction by scale factor 13\frac{1}{3}.
(edited 7 years ago)
Original post by Dapperblook22
I thought it would be the most intuitive, as this just needs rearranging. Each to their own methods however :tongue:


Ye at first glance it does look like a stretch in y direction as a lot of people did, but when you see that the 9 has changed to a 1 you know something not right! This is what I did:

So we started with y=sqrt(x^2+9)
and went to y=3*sqrt(x^2+1)
Ignore the y for now.
Square both equations to get x^2+9 -> 9*(x^2+1)
Then we get x^2+9 -> 9x^2+9
ignore the 9 and look what happened to x
We went from x^2->9x^2
We want to see what happened to x, not x^2
so next sqrt both, and we end up with:
x-> 3x, therefore a stretch by a third in x direction!
Original post by wil_is_he
Ye at first glance it does look like a stretch in y direction as a lot of people did, but when you see that the 9 has changed to a 1 you know something not right! This is what I did:

So we started with y=sqrt(x^2+9)
and went to y=3*sqrt(x^2+1)
Ignore the y for now.
Square both equations to get x^2+9 -> 9*(x^2+1)
Then we get x^2+9 -> 9x^2+9
ignore the 9 and look what happened to x
We went from x^2->9x^2
We want to see what happened to x, not x^2
so next sqrt both, and we end up with:
x-> 3x, therefore a stretch by a third in x direction!


yh dont think your right
Original post by wil_is_he
Ye at first glance it does look like a stretch in y direction as a lot of people did, but when you see that the 9 has changed to a 1 you know something not right! This is what I did:

So we started with y=sqrt(x^2+9)
and went to y=3*sqrt(x^2+1)
Ignore the y for now.
Square both equations to get x^2+9 -> 9*(x^2+1)
Then we get x^2+9 -> 9x^2+9
ignore the 9 and look what happened to x
We went from x^2->9x^2
We want to see what happened to x, not x^2
so next sqrt both, and we end up with:
x-> 3x, therefore a stretch by a third in x direction!


That's another good way of doing it. It was also that pesky 9 which spurred me to think of rearranging :tongue:. As long as you put down a correct way of doing it, then there should be no worries if the answer is correct :wink:
Original post by Rowan396
I beleive part d), the vector was (k,0), and the answer (the one I got atleast) was -5.5


Because k is a vector it is negative of what is in the equation... so it was --k which is +k... if you look at the graph it gave you, it needed to move right not left so had to be positive (just to check)
Original post by zzxxDash53xxzz
yh dont think your right

Sorry to hear that because you got it wrong then! :smile:
Reply 132
Avatar for dgkjhl
dgkjhl
2
How did you get -2 for a and 10 for d for the arithmetic series question? I got some long numbers like 10.1756 and when I plugged them into the formula I still got 8 so my final answer for the sum question was something like 138?
Original post by Myachii
Allow me to explain myself:
You could do the sum of the first three numbers using the formula (which is what I presume you used), or you could just figure them out (26, 24, 22) because it was an arithmetic series so subtracting two wasn't that hard :P

I said it was like using a sledgehammer to crack a nut because if you used the formula to calculate the sum of the first three, you made yourself a hell of a lot more work and more room for error.


Or just add 28 to the sum of the u2 and u3 which was already given :redface:
Original post by zzxxDash53xxzz
yh dont think your right


It is a correct way of doing it. If you can't see it this way, then look at my way attached above that gives the same answer :smile:
Reply 135
Avatar for 1120015
1120015
Original post by jake4198
Predicted Grade Boundaries

A - 61
B - 56
C - 51

Was easier than last year but not the easiest paper there's been.


Hey

I think I messed up both C1 and C2 papers and I am very upset about my self. I was wondering, to get an overall B grade in AS maths what do you need to get across all papers inclucding M1? And what would you need to get a C overall? Please reply.
Original post by zzxxDash53xxzz
yh dont think your right


Neither did I, but it checks out.
RIP my fellow y direction brother <3
Original post by 1120015
Hey

I think I messed up both C1 and C2 papers and I am very upset about my self. I was wondering, to get an overall B grade in AS maths what do you need to get across all papers inclucding M1? And what would you need to get a C overall? Please reply.


Define "messed up"
Original post by wil_is_he
Because k is a vector it is negative of what is in the equation... so it was --k which is +k... if you look at the graph it gave you, it needed to move right not left so had to be positive (just to check)


In x isnt it the opposite, so moving right it a negative value?

Either way im sure it was (k,0) not (0,k) like in the OP
(edited 7 years ago)
Original post by 1120015
Hey

I think I messed up both C1 and C2 papers and I am very upset about my self. I was wondering, to get an overall B grade in AS maths what do you need to get across all papers inclucding M1? And what would you need to get a C overall? Please reply.


For a B overall you need 70% UMS overall the AS level, meaning if you were to get 100% in M1, you would only need 55% in C1 and C2
(edited 7 years ago)

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