Ap3 - This sign shows AB in parenthesis + a body shift to show the first expression is equal to the second expression with BC in parenthesis. (We liked Tom Krohn's sign and liked the concept. We decided to enhance his sign by adding the body shift to show the two separate expressions.)
Ap4 - The sign shows that after performing an operation within the parenthesis, two numbers become one in each of the two separate expressions. We don't know if this will work effectively due to the time lag of interpreting. Also, it may not be comfortable to use this form of the sign(it may look or feel awkward). That is why we decided to leave two signs for the Deaf community and guest interpreters to choose from.