化简求值:3(xy-y2)-[-xy+2(y2+xy)]+2,其中x=-1 2 ,y=-1.

化简求值:3(xy-y2)-[-xy+2(y2+xy)]+2,其中x=-1 2 ,y=-1. 化简求值x2+3xy2y2分之-2x2-xy+y2,其中x=2y 化简求值:(-3分之一xy)2【xy(2x-y)-2x(xy-y2)】,其中x=-3,y=2 化简求值 (2xy)2(x2-y2)-(-3xy)3+9x2y4-9x4y2,其中x=-1,y=1化简求值分为两步 5x2-3xy-4y2-11xy+(-7x2)-(-2y2),其中x2+y2=7,xy=-2,求值 3xy²-[xy-2(xy-3/2x²y)+3xy²]+3xy²,其中x=3,y=-1/3 化简求值 化简求值-2分之1(xy-x2)+3(y2-2分之1x2)+2(4分之1xy-2分之1y2),其中x=-2,y=2分之1 (2xy-3)(2xy+3)+(xy+3)^2化简求值 x=1/5 y=-2 化简并求值,已知,x=2-根号3,y=2+根号3,求x2+3xy+y2的平方根 化简求值：【4（xy-1）²-(xy+2)(2-xy)】÷¼xy,其中x=-3,y=1/5 化简并求值 xy-2{xy-[3x²y-(xy²+0.5xy)]+4x²y},其中x=1,y=-2 化成最简分式:6x2-7xy-3y2分之2x2+xy-6y2 先化简再求值:(-1/3xy)2·[xy(2x-y)-2x(xy-y2)],其中x=-3/2,y=2快 已知x2+xy=3,xy+y2=-2,则2x2-xy-3y2= 已知x2-3xy=-5,xy+y2=3,求x2-2xy+y2. 化简求值:[4(xy-1)²-(xy+2)(2-xy)]÷ -1/4 xy,其中x=-2,y=1/5注意：是-1/4xy (3xy-9x2-2y2-6xy)-(6x2+2xy-3xy-y) 思考题：先化简,再求值：(xy-y2)÷x2-2xy+y2/y×x2-y2/y2,其中x=1/2,y=-1