How to represent a decimal number in ternary or base $3$ number system?

I need to convert a decimal number into base $3$ number.

$47_{10} ~~\mbox{is}~~ 1202_{3}$.

But how do you represent a negative number in base $3$ notation like $-297$?

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Prefix it with a minus sign? $-102000_3$? – Daniel Fischer Sep 17 '13 at 12:43
A similar question here math.stackexchange.com/questions/189596/… – Ömer Sep 17 '13 at 12:45

Just put a minus sign in front of it. By definition, in base 10 $47 + (-47) = 0$; therefore, $1202_3 + (-1202_3) = 0$ and so $-47_{10}$ is $-1202_3$.