12x^2+xy-6y^2答案是（3x+3y）（4x-2y）吗?

(x-2xy)*(-xy+2y*y)-(3x*x-2xy)(x-9xy+6y*y)答案应为-2x-x*x-3x， 12x^2+xy-6y^2答案是（3x+3y）（4x-2y）吗? 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 若正实数x,y满足2x+y+6=xy,则xy的最小值是?答案是18, 若y=3xy+x,求代数式2x+3xy-2y/x-2xy-y的值 答案是3还是3／5 因式分解207x^3y^2-12x^5-27xy^4答案是-3x(2x^2+3y^2-9xy)(2x^2+3y^2+9xy), 因式分解:12xy^2(y-x)+xy^3(x-y)+4x^2y(x-y) 已知xy²=-6,求xy(x^3y^7-3x^2y^5-11.5y)的值答案是2013 求完整过程! 已知y-x-3xy=0,求12x-14xy-2y除以x-2xy-y的值 急!等答案~~~（最好说明过程） 因式分解 x-xy+3y-3x 2x+xy-y-4x+5y-6 已知df(x,y)=(2y^2+2xy+3x^2)dx+(4xy+x^2)dy,求f(x,y)答案是2xy^2+x^2y+x^3+C 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^2+3xy+2y^2/x^2+2xy^2 怎样因式分解?答案是变成(x+2y)(x+y)/xy(x+2y),是怎么化的? (x+y)(x-y)-(2xy+3y)平方平方是(2xy+3y)的 1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y) 化简：x-y/x+3y÷x^-y^2/x^2+6xy+9y^2-(xy/x+y) 若x^2+xy-2y^2=0,则(x^2+3xy+y^2)/(x^2+y^2)=?答案是5/2或-1/5 若x/y=2,求7x²-3xy+2y²/2x²-3xy+7y²的值 答案是8/3