Answer:
729 and -2187 are the next on the list
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Step-by-step explanation:
Given
9,-27,81, -243,..
Required
Determine the next two numbers
The first step is to determine the formula that guides the pattern
Start by expressing all elements in the pattern as a base of -3
This gives:

Check if it corresponds with the given pattern

Let the above expression reflect their position in the pattern

By comparing each element;
We have that

The next two numbers is when n = 5 and n = 6
When n = 5



When n = 6



Hence;
<em>729 and -2187 are the next on the list</em>