根据已知条件,得：a=2分之11/2+b+3=0b=-3-1/2=-7/2（-a²+3ab-1/2b²）-（-2a²+4ab+1/2b²）=-a²+3ab-b²/2+2a²-4ab-b²/2=a²-ab-b²=1/4+7/4-49/4=-41/4=-10-1/4（-10...