3xy乘以[6 xy-3(xy-1/2x的平方y)]

3xy乘以[6 xy-3(xy-1/2x的平方y)] (-3xy+2xy)-(4xy+xy) 3xy(x^2y-xy^2+xy)-xy^2(2x^2-6xy+2x)过程 3xy(x^2-xy^2+xy)-xy^2(2x^2-xy+2x) （X-3xy+4xy-y）-[-2x-2（xy-3/2xy）-y]+6xy的过程 xy-2{xy-[3x^2y-(4xy^2+0.5xy)]+4x^2y}+6xy^2 [6xy-3(xy-1/2x的平方y]/3xy=? 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(9x²y-6xy²)÷3xy ②(3x²y-xy²+2分之1xy)÷(-2分之1xy) 【x(xy-xy)-y(x-xy)】÷3xy 2x²y-3(2xy-xy)-xy 因式分解X^3-2xy+xy^2 (X-3Y)乘以(-3XY)= -3(2x^2-xy)+4(x^2+xy-6) 1-(3xy-x)+【-2(2x+3xy)】 4(x²+xy-6)-3(2x²-xy) -3(2x²-xy)+4(x²+xy-6) 计算3xy[2xy-x(y-2)+x-1]