1/(a-x)-1/(a+x)-2x/(a²+x²)+4a²x/[(a²)²-(x²)²]
=[a+x-(a-x)]/(a²-x²)-2x/(a²+x²)+4a²x/[(a²)²-(x²)²]
=2x/(a²-x²)-2x/(a²+x²)+4a²x/[(a²)²-(x²)²]
=2x[(a²+x²)-(a²-x²)]/[(a²)²-(x²)²]+4a²x/[(a²)²-(x²)²]
=4x³/[(a²)²-(x²)²]+4a²x/[(a²)²-(x²)²]
=4x(a²+x²)/[(a²)²-(x²)²]
=4x/(a²-x²)