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

1/3 + 1/5 = 8/15.

step-by-step explanation:

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