Hi there!
To find the answer, you divide one of the numbers by 3, and some others by -3.
I can show you how to do so! :D
243 ÷ -3 = -81
-81 ÷ 3 = 27
27 ÷ 3 = 9
Next three terms -
9 ÷ 3 = 3
3 ÷ 3 = 1
1 ÷ 3 = 0.3333, the 3 is repeating over and over again
I think this is the answer, based off my notes :)
That's your pattern!
Hope this helps!
Message me if you need anything else, I'd be happy to answer any other questions! :D