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core maths c12 10 jan 2017

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Original post by mr.holmes
i got 2 values for y since it will be a quadratic equation. i basically solved it by substitution since the gave as the what is Y is equal to.


It was a quadratic equation??
Original post by Sumaiyya1999
The ans for the part a wasnt y/2 it was y - 2 and after solving i got 3 for y and 27 for x

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Well either you messed up in part A or I did lol. I probably did cuz I was getting the same y expression in both questions.
Original post by mr.holmes
i got 2 values for y since it will be a quadratic equation. i basically solved it by substitution since the gave as the what is Y is equal to.


Wasn't a quadratic equation.
Original post by Fasih178
Well either you messed up in part A or I did lol. I probably did cuz I was getting the same y expression in both questions.

but did you get a quadratic equation for it?
Original post by Fasih178
Well either you messed up in part A or I did lol. I probably did cuz I was getting the same y expression in both questions.


I actually opened up the log so for me log3(x/9)= log3(x) - log3(9) since log3(x)=y and log3(9)= 2 so I got y-2
There are no jan papers for gce
C12 papers are only for IAL
Original post by mr.holmes
but did you get a quadratic equation for it?


Nope, the question said 'hence or otherwise' I chose the otherwise part since I was pretty dubious about my answer to part A. But that might be why I didn't get a quadratic equation. At the end of the day there was only one solution and that was 81.
Original post by Sumaiyya1999
I actually opened up the log so for me log3(x/9)= log3(x) - log3(9) since log3(x)=y and log3(9)= 2 so I got y-2


That's definitely the correct answer. Why on earth didn't I think of that dammit
But shouldn't u get a quadratic equation if u choose otherwise cuz it was give 2log3 (x) which becomes log3 (×^2) so u end up with a quadratic equation in x

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for tan ( Qtheta -10) i got 1.3 and 181.3 ...

while for barrels i got 39600.. litres.

for 1 barrel was 1970 litres..
Original post by Fasih178
Nope, the question said 'hence or otherwise' I chose the otherwise part since I was pretty dubious about my answer to part A. But that might be why I didn't get a quadratic equation. At the end of the day there was only one solution and that was 81.

but they asked you to find the value for x or what exactly?
are you sure from your answer?
i thought we use the y for substituting in the equation
I actually got 1.3 and 91.3
And dor the barrels i got 34480 litres

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Original post by Sumaiyya1999
But shouldn't u get a quadratic equation if u choose otherwise cuz it was give 2log3 (x) which becomes log3 (×^2) so u end up with a quadratic equation in x

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Umm it was 2log3 (x/9) wasn't it? And the other term was log3 (√x) I recall.
how is it possible to get 91.3

not possible because tan is positive in 3rd quadrant and 3rd quadrant is angle greater than 180.

i wrote (180 + 11.30) minus 10

to get 181.3
Yes i just remembered guess i am gonna lose 1 or 2 marks for it

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Original post by Sumaiyya1999
Yes i just remembered guess i am gonna lose 1 or 2 marks for it

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so is my answer right....
Original post by Fasih178
Umm it was 2log3 (x/9) wasn't it? And the other term was log3 (√x) I recall.


O yes but that way way also u should get a quadratic equation cuz (x/9)^2 is x^2/9^2

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Original post by Fasih178
Umm it was 2log3 (x/9) wasn't it? And the other term was log3 (√x) I recall.


yes and what was y
the one given in the question?
Original post by mr.holmes
yes and what was y
the one given in the question?


i got y= 1/5 and x= 81...
and i think these are correct.. becuz i confirmed it with ma fellows
Original post by mr.holmes
but they asked you to find the value for x or what exactly?
are you sure from your answer?
i thought we use the y for substituting in the equation


We could have substituted y or solved the question merely through logarithm laws which is what I did.

Just think about it if x=81, log3(81) gives 4 which is y. And therefore the expression which Summaiya got for log3 (x/9), y-2, is equals to 2. If you sub x=81 in, you end up with y-2 equaling 2.

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