Is it necessary to do all of the calculations to determine the sign of the product?

Depends on the formula, but with most cases yes, because you may have -3 as an answer, but adding only 4 makes it positive.

There are some cases where you could look at it and know the sign, like if I am adding -100 and -93, I know the answer will be negative

5/12, or 5: 12

step-by-step explanation:

(-5,-28)

i graphed to on desmos.