(-x^2+3xy-0.5y^2)-(-0.5x^2+4xy-3/2y^2)
=(-x^2+3xy-0.5y^2)+0.5x^2-4xy+3/2y^2
=-0.5x²-xy+y²（a-2)^2+|2b+a|=0,3a-2b=( )（a-2)^2+|2b+a|=0所以（a-2)^2=0，|2b+a|=0a-2=0,2b+a=0a=2,b=-13a-2b=6+2=8