3xy^2÷（-6y^2/x）^3×（12y/x）^2

（X-3xy+4xy-y）-[-2x-2（xy-3/2xy）-y]+6xy的过程 化简求值x-4y/2x-7xy+3y×x-2xy-3y/2x+3xy-2y÷3x-6y/4x-4xy+y,其中：x=1999,y=-1 计算(3x^3y-x^2y+1/2xy)÷(-1/2xy） ①(9x²y-6xy²)÷3xy ②(3x²y-xy²+2分之1xy)÷(-2分之1xy) 化简：x-y/x+3y÷x^-y^2/x^2+6xy+9y^2-(xy/x+y) (-4x(2xy+3xy^2)+12(x^2y)^2y^3)÷（-6xy） 1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) 5xy^2-{2x^y-[3xy^2-（xy^2-2x^2y）]/（-1/2xy）} 化简!1、（x^2-xy）+xy+y^2 2、3（x^2-xy）-xy+y^2 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 （-1/2xy）（2/3x^2y-3/2xy^2+6/5y) 几道数学题：x-x^2分之x^2-1×1-y分之xy-x,（xy-x^2）÷xy分之x-y,x^2+x分之x-3÷（x^2-6x+9）谢谢! x^2-xy-6y^2+3xy+y+2 4xy-[(x²+5xy-y²)-(3xy-1/2y)]x=3,y=-6 x²-y²+5x+3y+4（x+y-2xy)(x+y-z)+(xy-1）² 计算：1.（x-1)^2+2(1-x) 2.(x-y)/(x+3y)÷(x^2-y^2)/(x^2+6xy+9y^2)-2y/(x+y）1.（x-1)^2+2(1-x)2.(x-y)/(x+3y)÷(x^2-y^2)/(x^2+6xy+9y^2)-2y/(x+y） xy-2{xy-[3x^2y-(4xy^2+0.5xy)]+4x^2y}+6xy^2 计算：3xy[2xy-x（y-2）+x]