已知2(x﹢y)﹦-6,xy﹦1,求(x﹢2)-(3xy-y) (怕麻烦,剩下的直接打字) ,已知当X等于负1,A乘X的3方加BX加5等于负9,那么当X等于负1,A乘X的3方加BX加5的值为 某单位在5月份外出7天,假设七天日期之和为63的

已知实数xy满足x²﹢y²-xy+2x-y+1=0求xy 已知x-y=6,xy=-1,求(2x+3x-2xy)-(x+4y+xy)-(3yx-2x+2y)的值 已知:x/y=-2,求x^2-2xy-3y^2/x^-6xy 已知实数xy,满足10x²-2xy+y²+6x+1=0,求x+y 已知X+y=6,xy=7 求x^2y+xy^2=已知X+y=6,xy=7 x^2y+xy^2 已知xy/x+y=6,求3x-2xy+3y/-x+3xy-y的值. 已知(xy)/(x+y)=6求(3x-2xy+3y)/(-x+3xy-y)的值. 已知3/(x-y)=1/xy 求(-x-2xy+y)/ (2x+3xy-2y) 已知xy-x-y=11,求(xy-1)^2+(x+y-2)(x+y-2xy)的值. 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=-2,求代数式-5（x+y)+(x-y)+x(xy+y)的值 .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 已知x+y=6,xy=4,求x^2y+xy^2的值~ 已知x/y=2,求 [x^2-xy+3xy^2 ] / [ x^2+xy+6y^2]的值 已知x(x-1)-(x²-y)=-3,求(x²y+xy²)÷xy-2y 已知xy满足(x+1)^2+y-2=0 求代数式-2xy+(1/2x^2y^2-3y)*2x+6xy 已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) 已知xy+x-y+1=6,(1-x^2)(1-y^2)+4xy=48,求xy-x+y+1的值!一定要今天