Answer:
-3, -9, and -15.
Explanation:
To identify the pattern, let's examine the differences between consecutive terms:
21 - 15 = 621−15=6
15 - 9 = 615−9=6
9 - 3 = 69−3=6
We can see that the differences between consecutive terms are all equal to 6.
Following this pattern, the next three numbers would be:
3 - 6 = -33−6=−3
-3 - 6 = -9−3−6=−9
-9 - 6 = -15−9−6=−15
So, the next three numbers in the pattern are -3, -9, and -15.