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C3 functions

http://www.examsolutions.net/a-level-maths-papers/Edexcel/Core-Maths/Core-Maths-C3/2012-January/paper.php#Q7

7b

why isn't this right?
let
x=12y−1x=\dfrac{1}{2y-1}

x(2y−1)=1x(2y-1)=1

2y−1=1x2y-1=\frac{1}{x}

2y=1x+12y=\frac{1}{x}+1

y=1x+12y=\dfrac{\frac{1}{x} +1}{2}
The last step you took was halve both sides, right? If we take the half out, so we're left with 0.5(1/x+1), we can then expand out properly to get y=1/2x+1/2=(1+x)/2x
Reply 2
Avatar for bigdonger
bigdonger
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Original post by an_atheist
The last step you took was halve both sides, right? If we take the half out, so we're left with 0.5(1/x+1), we can then expand out properly to get y=1/2x+1/2=(1+x)/2x


oh ok i see
Reply 3
Avatar for B_9710
B_9710
18
You are correct.
Reply 4
Avatar for Zacken
Zacken
22
Original post by bigdonger

why isn't this right?



Why do you think it's not right?
Reply 5
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bigdonger
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Original post by B_9710
You are correct.

ah...
Original post by Zacken
Why do you think it's not right?


because it wasn't the same as the "most simplified" version of the answer which was in the solution video.
Reply 6
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Zacken
22
Original post by bigdonger
Because it wasn't the same as the "most simplified" version of the answer which was in the solution video.


Alright, can you see how to simplify it down now?
Reply 7
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bigdonger
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Original post by Zacken
Alright, can you see how to simplify it down now?


yes
Reply 8
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Zacken
22
Original post by bigdonger
yes


Great.

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