So instead of think all around +a -a and all that, think about the Aml as if it is the distance from origin.
Then realize it makes no difference if it is from [0,a] or [-a,a] since it is the same distance.
After that you can find FAml(x) shown from class notes.
obtain faml(x) given the range 0 to a
integrate it, get aml from -a to a BUT remember it is only validated from 0 to a.(PS. this is where i made a mistake)
