先化简2(1/2x^2—3xy—y^2)—(2x^2—7xy—2y^2),x=4,y=-2/3,求值

若1/X—1/Y=2,求3X-2XY-3Y/X-2XY-Y 计算3xy[2xy-x(y-2)+x-1] (-1/3xy)^2•[xy(2x-y)-2x(xy-y^2)] xy(xy+1)+xy+3-2(x+y+1/2)-(x+y-1)^2因式分解 (-3分之1xy)的平方×[xy(2x-y)-2x(xy-y的平方)] XY(XY+3)+(XY+4)+4(X+Y+1)-(X+Y+2) 若1/x-1/y=2,求3x-2xy-3y/x-xy-y的值3x-2xy-3y/x-xy-y 不好意思，是3x-2xy-3y/x-2xy-y .(x+y-2)(x+y-2xy)+(xy-1)^2 2x²y-3(2xy-xy)-xy 已知x—xy=5,xy—y=-3,求x+y—2xy的值. 已知:x+y=—3,xy=2,求-2(xy-3x)-2(2y-xy)的值 因式分解x^2y^2+x^2y+xy^2+3xy+x+y+1 (-x²+2xy-y的平方)-2(xy—3x²)+3(2y的平方-xy) 计算. 1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) 先化简,再求值:{xy(x²-3y)+3xy²}(-2xy)+x³y²(2x-y),其中x=-1/2,y=-5 x-3xy=—5,xy+y=3,求x-2xy+y的值 (-xy^-1)^2*(-xy^-2)^-3/(-x^2y^3) y^3+xy^2+2xy+x^2-1 因式分解