Convert from factored form to standard form d. $A(x)=(x+a)(x-a)$

Step 1 ：Convert the given factored form $(x+a)(x-a)$ to standard form.

Step 2 ：The standard form of a quadratic equation is $ax^2 + bx + c$.

Step 3 ：Expand the expression $(x+a)(x-a)$ to get the standard form.

Step 4 ：Upon expansion, we get $x^2 - a^2$.

Step 5 ：Final Answer: The standard form of the given factored form is \(\boxed{x^2 - a^2}\).