why standard form is only work with positive numbers?

Question

Example:
A number expressed in standard form is written as A x 10^n, where 1<= A < 10 and n is a positive or a negative integer.
why A is only positive integer between 1<= A < 10 ? why A cannot be in negative numbers?
I hope you can help me..
Tq very much!

Answer 1

You are wrong with this, A can very well be a negative number.
otherwise it would be impossible to have negative numbers .

negative numbers exist in nature, for instance freezing is below zero degrees Celcius.

Answer 2

Standard form is mainly used in physical measurement therefore only makes sense to be positive. In fact, we can use exponential form such as B x 10^n (B can be negative) to express any numbers which could be found in your calculator.