化简：1/xy+1/(x+4)(y+4)+1/(x+8)(y+8)+1/(x+12)(y+12)+……+1/(x+4n)(y+4n) 别去复制!

化简:[4xy(x-y)^-1 + (xy^-1 - x^-1y)/(x^-1 + y^-1)] / (x+y)^2 (x+y)(x+y+2xy)+(xy+1)(xy-1)(x+y)(x-y)+4(y-1) XY(XY+3)+(XY+4)+4(X+Y+1)-(X+Y+2) 化简4xy-y-xy+x 已知xy>0,证明xy+xy/1+x/y+y/x>=4 1-2/x+y=xy,4y+6x=xy.求xy的解? xy>0,证xy+1/xy+x/y+y/x>=4 已知xy大于0求证xy+1/xy+y/x+x/y大于等于4 化简 2（xy-xy²+3）-（-4xy²+xy-1） 其中,x等于--4,y等于-3 化简xy-1-x+y 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 X(4y+1)-4xy因式分解 化简-12xy^2*1/3x^3y^4-x(2xy^2)^3 化简-12xy^2*1/3x^3y^4-x(2xy^2)^3 x方-xy+1/4y方 x-2xy-1+4y² x平方-xy+1/4y平方 (-2xy+2x+5y)-(3xy+2y-2x)-(x+4y+xy)其中x-y=4xy=-1