la-1l+lb+3l=0求b-a-0.5的值

la-1l+lb+3l=0求b-a-0.5的值

兩個非負數的和為0,則各自為0.所以a-1=0;b+3=0;所以a=1,b=-3所以b-a-0.5=-3-1-0.5=-4.5