How did Trade result in use of Negative numbers.
Negative numbers are believed to be a Chinese invention, inspired by their concept of duality in creation.
INTEGERS
The Chinese silk saw huge demand in the Roman empire by 200BC and the secret was kept with the Chinese. And hence there was a organized trade route from China to India to Persia and finally to the Mediterranean. This meant that trade in volumes began with strangers and hence the evolution of money instead of the barter system. And this needed to account for debt and finally negative numbers for bookkeepers.
Like the zero is attributed to the Hindus, negative numbers is given to the Chinese. The Chinese concept of duality or more often called Yin-Yang is central to their concept of balance between these forces for the existence of the Cosmos. The also had rods to represent positive and negative numbers and perform arithmetic.
The first consequence would be while adding a negative number to a positive number or debt to asset. These would give negative numbers when dealing with money. Still while applying to objects would result only in zero as you cannot take away more objects than what is there.
Negative numbers became popular in India approximately 600 AD after Brahmagupta gave the rules for negative numbers.
Multiplication with negative numbers would be meaningful in the common man’s world only when dealing with quantities that had direction or simply vectors.
The two places where negative numbers are used in Temperatures and Heights (Depths).
But, taking the square root of a negative number would finally make mathematics complicated and lead to what we know today as complex numbers.