x*2+y*2=13 xy=6 求x*4y*4的值

1-2/x+y=xy,4y+6x=xy.求xy的解? 诺x+y=6,xy=4 求(5x-4y-3xy)-(8x-y+2xy) x^+2xy+y^+4=16 x^-2xy+y^=16 求(3xy+6y^)+|x^-(2xy+2y^-3x^)|的值 已知x+y=6,xy=4,求x^2y+xy^2的值~ 当x-y=2xy时,求4x-3xy-4y/xy 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^2+y^2-4x+6y+13=0求(xy+y^2/5x^2-5xy+xy+y^2)·（5/x+y）-（y/x-y） 已知x-y=6,xy=-1,求(2x+3x-2xy)-(x+4y+xy)-(3yx-2x+2y)的值 已知x+y=4,xy=3,求4{xy+2y}+{6x-[2xy-y-3x}}的值 x+y=-4 若x+y=4 x-y=6 求xy(x^2+y)-y^2(xy+2x)-3xy的值求值 已知x+y=-2,求代数式(6xy+10y)+[4x-2(3xy+2y-x)] 已知:x/y=-2,求x^2-2xy-3y^2/x^-6xy 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? x+y=8,xy=-2,求(5xy+4x+7y)+(6x-3xy)-(4xy-3y)的值 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 求（3x^+y^-5xy）-【2x^-（-4xy-y^+7x^）】=? 已知13X^2-6XY+Y^2-4X+1=0,求(XY-X^2)^5的值. 已知13x^2-6xy+y^2-4x+1=0,求(xy-x^2)^3的值.