The pattern subtracts 1.5 for each number in the pattern. 3-1.5 is 1.5.
1.5 minus 1.5 is zero. 0 minus 1.5 is -1.5. -1.5 minus 1.5 is negative
3. If we apply this rule to the next value, it would be -3 minus 1.5
which is equal to 4.5. The value after that would be 6, applying the
same rule.
