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September 16, 2019, 08:04:27 am

Author Topic: Mathematics Question Thread  (Read 576907 times)  Share 

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Coolmate

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Re: Mathematics Question Thread
« Reply #4335 on: September 11, 2019, 10:16:43 pm »
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Thanks Rui! ;D ;D

Your explanation was very clear and I understood it!

Thanks also, fun_jirachi! ;D ;D That is a good point!
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Re: Mathematics Question Thread
« Reply #4336 on: September 11, 2019, 11:02:37 pm »
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Need help with working out this question:
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fun_jirachi

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Re: Mathematics Question Thread
« Reply #4337 on: September 11, 2019, 11:10:09 pm »
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You can think about it as the three points (-12, 4), (0, 0) and (12, 4) being on the parabola x2=4ay. Subbing in the first point or the third point will get you 144=16a, which tells you that the focal length a will be 9 metres. Hence, the answer is D.

Hope this helps :)
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Re: Mathematics Question Thread
« Reply #4338 on: September 11, 2019, 11:35:48 pm »
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Need help with working out this question:

Here's a visual aid to go with fun_jirachi's explanation.



The idea is that ultimately, no matter what it's going to be a parabola. So it's easier to just rotate the paper until it's oriented the same way as an \(x^2=4ay\) parabola. (Note that the vertex was chosen to be \((0,0)\) for the sake of convenience - you could try a different vertex and find that you'll get the same answer, but it's a needless trek.)