14
-22
There are infinitely many pairs of numbers that will add to 105.8 and infinitely many pairs of numbers that will multiply to 105.8 but there are no pair that will add AND multiply. I do not think there are larger sets, but I could be wrong. One example of a triplet adding and multiplying to the same number is 1, 2 and 3. They add to 6 and multiply to 6.
14
-46
6 and 2
2
22
-7 and +1
2 and 4
-6 and -20
0.316624791, -6.316624791
11
The two numbers that add up to 5 and multiply to -6 are 3 and -2. This is because 3 + (-2) = 1 and 3 * (-2) = -6. These two numbers satisfy both conditions given in the question.
14
They are -2 and -4
-22