（2x^2-4x-10xy)/( )=1/2-1-5/2y拜托各位了 3Q

1-2/x+y=xy,4y+6x=xy.求xy的解? [(xy+2)(xy-2)-2x^2y^2+4]/xy,其中x=10,y=-1/25 [(xy+2)(xy-2)-2x^2y^2+4]/xy,其中x=10,y=-1/25 已知x+xy=20,xy+x= -10,求下列代数式的值1.3-4x-4xy+1/2xy+1/2y 2.x-y3.x+2xy+y （-3x^y+2xy)-( )=4x^+xy -3(2x-xy)-4(-6+xy+x.其中x=1,y=-1 已知1/x-1/y=2,求3x+7xy-3y/2x-3xy-2y答案是1/x-1/y=2(y-x)/xy=2 得：x-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy)=xy/(-7xy)=-1/7 谁能帮我解释一下=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy) 是怎 已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) (x^3+3x^2-2xy^2+1)+(-xy^2+x^2-2X^3+2)+(x^3-4x^2*y+3xy^2-8)= (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1 若x-y=4,xy=1,求(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)= x-y=1,xy=2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 (1)已知x+y=6,xy=-3,x^2y+xy^2=(2)x*[2-(1/x)]+(x/x^2-2x)*(x^2-4) 先化简,再求值：-4x+7x-5-3x-6x+2,其中x=-2分之1 4xy-3x-xy先化简,再求值：-4x+7x-5-3x-6x+2,其中x=-2分之14xy-3x-xy+y+x-3xy-2y+2x+x,其中x=-5,y=-1 1.已知x+y=-4,xy=3,求5（2分之1xy+2y）+[6x-(2xy+y-3x)]的值2.已知（x+3）^2+|x-y+10|=0求代数式5x^2y-[2x^2y-(3xy-xy^2)-3x^2]-2xy^2-y^2的值 已知x-y=6,xy=-1,求(2x+3x-2xy)-(x+4y+xy)-(3yx-2x+2y)的值