-(3ab-a2)-{2a²-(3ab-b²)},其中a=－2,b=－1

-(3ab-a2)-{2a²-(3ab-b²)},其中a=－2,b=－1
-(3ab-a2)-{2a²-(3ab-b²)},其中a=－2,b=－1

-(3ab-a2)-{2a²-(3ab-b²)},其中a=－2,b=－1
-(3ab-a2)-{2a²-(3ab-b²)},
=-3ab+a²-2a²+3ab-b²
=-a²-b²
当a=－2,b=－1时
原式=-a²-b²
=-4-1
=-5

原式=-3ab+a²-(2a²-3ab+b²)
=-3ab+a²-2a²+3ab-b²
=-a²-b²
=-4-1
=-5

-(3ab-a²)-{2a²-(3ab-b²)}
=-3ab+a²-(2a²-3ab+b²)
=-3ab+a²-2a²+3ab-b²
=-a²-b²
=-(-2)²-(-1)²
=-4-1
=-5