To know this you first need to know the basic concept of sign multiplication:

If **minus(-) sign is outside the power** then it remains same if we multiply any number with this.

But **if minus(-) sign is inside the power** then it will be evaluated as:

**if minus(-) to the power is even then minus will become (+)**

**that is (-)**^{n} = (+) if n is even and

**if ****minus(-) to the power is odd then minus will remain same**

**that is (-)**^{n} = (-) if n is odd.

**In your question -A**^{2} minus sign is outside the power so the sign will remain same and if we put the value of A=3

**Then, we will get -3**^{2} = -9

Hope you understand :)