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Yeah, sorry about that, just a huge derp moment there. I was just trying to twist the numbers a bit, but as you can see I failed massively heh

Yes, I just graphed my solution and the question on Geogebra, and they intersect at y=0 i.e. I graphed y=5-2^(x+1)-x and y=1+2x-x^2-2^x I thought it was fine though because I tested x=1, the solution *embarassed*

Well, if you take it this way, ln of anything is always a value that is fixed, so whatever x is fixed at, ln is fixed. So in that line of working, Im basically saying that: 2 of the LHS = 1 of the RHS Therefore 1 of the LHS = 0.5 of the RHS. Because its an equation and balance needs to be...

The answer is much more evident there, and moreover, it is more evident that there is only 1 solution here since it is a linear function intersecting an exponential graph (in my simplified version)

I was able to algebraically simplify the expression into its simplest form of x=5- 2*2^x This is done by doing ln to both sides after you make the RHS a perfect square, then playing around with log laws and the numbers after that.

I thought to state rank you need 100 in them because I would be sure some 20 people will get 100 in the exam considering there are alot of contenders in each subject (except rare 4u math and english and languages). But it makes me happier I dont need 100 to state rank some subjects. What do...

Re: HSC 2012 Marathon :) Your in the right track barbenator BIG SPOILER HINT: in a sin (nt+alpha)+b, b = kt

Re: HSC 2012 Marathon :) There are 4 hints to tell you to use a trigonometric function. "Amplitude" "Period" "Inverse Trig value for v=0" "a sort of S.H.M." Im sorry if its not too clear though. Like I said, I thought of the premise on the top of my head, and it took me a while to figure out...

Re: HSC 2012 Marathon :) Yes very much so.

Re: HSC 2012 Marathon :) Ok, Ive got a good premise for a question. But I dont know enough to make the question more creative. But yeah here we go.

Re: HSC 2012 Marathon :) Ill edit one in as soon as I can think of one (a question)

Re: HSC 2012 Marathon :) Nice work both of you, now someone post a question!

Re: HSC 2012 Marathon :) Here is another question because no one decided to post one. http://www.codecogs.com/latex/eqneditor.php Use that link man, you dont even need to learn anything about latex to use it.

Re: HSC 2012 Marathon :) Ok since this thread is awesome, and its dead, I will revive it with a more reasonable question that is actually fun to do. I dont actually know the answer, but this is a question someone gave to me. In the exact wording and everything

://// Stupid mistake on my part. Yeah I got 4km/s now. When you find C, you have to subsitute x=10 000 not 3600. And when you do that, you get 4km/s

hmmm, I did my way and I got C=0 My answer in the end was: 20/3 km/s I got the pair by noticing that x is the distance from the earth's surface. Just when the rocket is fired, it is starting to rise at 5km/s however at that point it is 6400km from the centre of the earth. Since C is just a...

when x=6400, v=5

The answer definitely should be 1. Either we are all wrong, and the textbook defies simple trig logic. Or the answer is wrong/misprint etc. Test it, enter any radian value into the expression, and you should always get 1. Another way of look at it is this. If you graph sin(pi-x), the original...

:| Ive been trying for about 15 mins at a question I cant solve. Ah well, it was fun trying

Just clarifying, so initially there is 500L of salty water in the tank with 20g/L salt concentration. And fresh water 2g/L salt is flowing into the tank at 8L/min? If so I will start solving it