# Edexcel A2 C3 Mathematics 12th June 2015Watch

This discussion is closed.
3 years ago
#2081
(Original post by imedico10)
Can someone explain 7b please
This is how I explained it to the last guy. But seriously... go to bed.
(Original post by JizzaStanger)
First do a sketch to determine roughly where the graphs touch. Because the one of the functions is |f(x)|, you use the sketch to determine whether you're in the section where |f(x)| = -f(x) or the section where |f(x)| = f(x).

Now you've determined that with a sketch (from the fact that you would otherwise have to take the square root of a negative number, it's in the region where |f(x)| = -f(x) ). You should now set -f(x)=g(x), and follow the method again. It will get you k = +/- 2a.

You can determine whether k = 2a or -2a by using your sketch again. The question tells you that g(x) cuts |f(x)| at another point, Q. You'll find that one value of k makes it impossible for the curves to cross at Q and that one makes it possible. The one that makes it possible is, of course, 2a.

I hope this clears it up!
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3 years ago
#2082
c3 june 13 was anal without lube, I feel unprepared now after doing that paper having done all the solomon papers and all the edexcel papers pre-june 13
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3 years ago
#2083
(Original post by imedico10)
Can someone explain 7b please

Sorry... I need to elaborate on 'the method.'

(Original post by JizzaStanger)
First do a sketch to determine roughly where the graphs touch. Because the one of the functions is |f(x)|, you use the sketch to determine whether you're in the section where |f(x)| = -f(x) or the section where |f(x)| = f(x).

Now you've determined that with a sketch (from the fact that you would otherwise have to take the square root of a negative number, it's in the region where |f(x)| = -f(x) ). You should now set -f(x)=g(x), and follow the method again. It will get you k = +/- 2a.

The method is as follows: Set -f(x)=g(x). Because g(x) is a tangent to |f(x)| in the region where |f(x)|=-f(x), g(x) will only touch |f(x)| and not cross it at P. This means the equation -f(x)=g(x) (it will be a quadratic) will have one repeated solution. This means the discriminant of the equation = 0. Solve the equation: discriminant = 0 to find k.

You can determine whether k = 2a or -2a by using your sketch again. The question tells you that g(x) cuts |f(x)| at another point, Q. You'll find that one value of k makes it impossible for the curves to cross at Q and that one makes it possible. The one the makes it possible is, of course, 2a.

I hope this clears it up!
0
3 years ago
#2084
(Original post by veniceswan)
Hi does anyone know when the graph is shifting to the right and left or up and down? For example, for normal equations like 3x, does it means stretch up and down by a factor of 3?
Also can somebody help me with this 6c on 2014(r). I don't understand why 2x doesnt get why isnt 2x squared?
Thanks
f(x+a) is shift to the left by a
f(x-a) is shift to the right by a
f(x)+a is shift upwards by a
f(x)-a is shift downwards by a

-f(x) is reflection in x axis
f(-x) is reflection in y axis

af(x) is a vertical stretch by a
1/a f(x) is a vertical compression by a

f(ax) is a horizontal compression by a
f(1/a x) is a horizontal stretch by a

and for 6c in 2014
its because g(x)+g(x^2)+g(x^3)
not g(2x)+g(2x^2)+g(2x^3)

only the x is getting squared, not the number in front of it.
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3 years ago
#2085
(Original post by Hudl)
c3 june 13 was anal without lube, I feel unprepared now after doing that paper having done all the solomon papers and all the edexcel papers pre-june 13
take a deep breathe…
i nearly cried when i done it……….

then i check boundaries

50 for an A
57 for an A*
with a special notice on the mark scheme basically saying 'sorry we f*ked everyone over
1
3 years ago
#2086
can't sleep so thought I may as well browse this for inspiration haha

Posted from TSR Mobile
1
3 years ago
#2087
(Original post by Hudl)
c3 june 13 was anal without lube, I feel unprepared now after doing that paper having done all the solomon papers and all the edexcel papers pre-june 13
Yep, currently on q6 on that paper... damn, it has demotivated me quite a bit. Even the low grade boundaries wouldn't have saved me so lemme pray that edexcel is nice this year.
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3 years ago
#2088
(Original post by Hudl)
c3 june 13 was anal without lube, I feel unprepared now after doing that paper having done all the solomon papers and all the edexcel papers pre-june 13
..
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3 years ago
#2089
https://docs.google.com/file/d/0B1Zi...lBJ/edit?pli=1
can somone explain 8a?
please
i dont get it
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3 years ago
#2090
So people who are still here, what time are y'all planning to catch some sleep?
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3 years ago
#2091
(Original post by marco cb)
So people who are still here, what time are y'all planning to catch some sleep?
This is the first exam im considering staying up..got 7 more PP to skim through...
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3 years ago
#2092
(Original post by marco cb)
So people who are still here, what time are y'all planning to catch some sleep?
they are not!!!
it is not a good idea to catch some sleep before an exam ...
0
3 years ago
#2093
(Original post by suyoof123)
This is the first exam im considering staying up..got 7 more PP to skim through...
hopefully you catch some sleep during the exam ...
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3 years ago
#2094
https://docs.google.com/file/d/0B1Zi...lBJ/edit?pli=1
its the jan 15 c34 ial paper
can somone explain 8a?
please
i dont get it
0
3 years ago
#2095
(Original post by TeeEm)
hopefully you catch some sleep during the exam ...
Yeah , my random head movements sleeping with the pen in my hand will draw the correct solutions

Ok ok mr grumpy cat I'll sleep in 5 mins

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3 years ago
#2096
Got a question from that june 13 paper, not gone to bed yet as trying to understand where I flawed. There are a few algebraic errors due to silly mistakes. Sill managed an A* but only got 58.

I'm confused as to why you found the maximum value for the denominator, if we want the minimum value for V shouldnt the value on the denominator be as small as possible so -25 in other words, that way you get 21/-25 which is smaller than 21/25?

for the velocity question part b q8 June 2013

EDIT

Also within the range we're given 0 < X < 150 we cant have cosX as 1
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3 years ago
#2097
(Original post by Tplox)
https://docs.google.com/file/d/0B1Zi...lBJ/edit?pli=1
its the jan 15 c34 ial paper
can somone explain 8a?
please
i dont get it
Put t=0 into the function to get the maximum value of V (=23000) we know that as t goes to infinity, e^-0.1t and e^-0.2t go to zero, hence the graph's asymptote is at V=0+0+1000, V=1000 is the minimum value of V, but V only reaches 1000 at infinity so you must put V>1000 not V>=1000, so final answer is 1000<V=<23000
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3 years ago
#2098
(Original post by A1d9a9m7)
can't sleep so thought I may as well browse this for inspiration haha

Posted from TSR Mobile
u need sleep bro...its key
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3 years ago
#2099
Just woke up... Anyone else here?
0
3 years ago
#2100
(Original post by anonwinner)
Just woke up... Anyone else here?
yeah im here
0
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