1/2x²+xy+1/2y² x+y=2 xy=1/2

化简求值3x²y-[2xy-2（xy-3/2x²y)+xy]+3xy²其中x=3、y=-1 若x=1/2,y=1 求x(x²+xy+y²)-y(x²+xy+y²)+3xy( 已知实数xy满足x²﹢y²-xy+2x-y+1=0求xy 若x+y=10 xy=-1 则x²+y²=(x+y)²-2xy= 已知x+y=2,xy=1/2,求x³y+2x²y²+xy³ 已知X²+Y²+X²Y²-4XY+1=0 求:（X-Y)^2008-(XY)^2 1/x+1/y=5,求2x-3xy+2y/x²+xy+y的值 已知(x+1)²+|y-1|=0,求2(xy-5xy²)-(3xy²-xy)得值 因式分解xy²-2xy+x+2y-1 已知：xy+x=-1，xy-y=-2． 化简并求值 xy-2{xy-[3x²y-(xy²+0.5xy)]+4x²y},其中x=1, (x+y-2xy)(x+y-2)+(1-xy)²