-2（ab-3a的平方）-[2b的平方-（5ab+a的平方)+2ab
=-2(ab-3a²)-[2b²-(5ab+a²)+2ab]
=-2ab+6a²-2b²+(5ab+a²)-2ab
=-2ab+6a²-2b²+5ab+a²-2ab
=7a²+ab-2b²