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# Confusion watch

1. Thnz Smaug

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2. How did you get y=3 from x=4 in 3y = 6-3x? As I see it, 3y = 6-12 = -6 = 3, so y = 1 or 4 or 7.
You can make equation 2 simpler by saying 3x+3y = -6 (mod 9) => x+y = -2 = 1 (mod 3), but it's not necessary - just makes it a bit neater.
3. (Original post by MV=PT)
Ah yea, my bad I got to the 3 and incorrectly left it as the answer. Regardless of that mistake, if in the exam I went ahead with inputting the values into the second equation (which is completely legit, right ?) how would I get the right answer ?
It's sort of legit. You don't actually have enough information from the second equation alone to specify y more than up to correctness mod 3, because everything gets multiplied by 3; the second equation is precisely equivalent to the statement that x+y=1 (mod 3). You need to use the first equation again to narrow down the possibilities.

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Updated: April 11, 2013
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