已知x²-xy=21,xy-y²=-12,分别求式子x²-y²与x²-
已知x²-xy,xy-y²=-12,分别求式子x²-y²与x²-2xy
已知x²-xy=21,xy-y²=-12,分别求式子x²-y²与x²-
已知2x-y=10,求式子[(x^2+y^2)-(x-y)^2+2y(x-y)]/4y (4xy-2y²)/4
已知x:y=3:2,求(x²+3xy)/(xy+2xy)
已知x²-7xy+12y²=0求x²-xy+y²/2xy的值
已知x/y=3,求(x²+2xy-3xy²)/(x²-xy+y²)
已知x-y=根号5,xy=二分之一,求x²-xy+y²
已知x²+y²-8x+6y+25=0,求(x-y+4xy/x-y)(x+y-4xy/x+y)
已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y²
已知x+y=1,xy=-二分之一,求x(x+y)(x-y)-x(x+y)²
已知实数x,y满足条件|2x+3y+1|+(x+3y+5)²=0,求式子(-2xy)²×(-y
已知x/y=3,求x²+2xy-3y²/x²-xy+y²