已知x+y=3,xy=1,则4x+3xy+4y=

已知x+y=3,xy=1,则4x+3xy+4y= 已知xy/x+y=1/2,则代数式3x-5xy+3y/-x+3xy-y= 已知x+y=4,xy=3,则-xy-xy= .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 已知x y=1,xy=-3,求2xy-4x 4(y-2(xy-x)) 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2/x-1/y=3,则(2y-x+4xy)/(3x-6y-5xy)=? 已知1/X-1/Y=5 ,则x-2xy-y/4x+3xy-4y 已知xy=-3,x+y=-4,则x²+3xy+y²=? 已知x/y=3/4 ,则3xy-2y/2x+4xy=? 已知x+y=3,xy=1,求代数式5xy+4x+7y+6x-3xy-4xy+3y的值. 已知XY是实数,X/3+Y/4=1,则XY的最大值 解析 已知x²-3xy+4x=3,y²+xy-4y+7=0,则xy-1/2(x²+y²)的值为 已知x+y=5,xy=-1,则（3x-4y+2xy）-（2x-5y+5xy）=? 已知x+y=5,xy=-1,则（3x-4y+2xy)-(2x-5y+5xy)=_______ 已知x-y=3,xy=1,求（-2x+2x+3y)-(3xy+2y-2x)-(x+4y+xy) 已知/X-Y-1/+(XY+3)的平方=0,求(-2XY+2X+3Y)-(3XY+2Y-2X)-(X+4Y+XY)的值!已知/X-Y-1/+(XY+3)的平方=0,求(-2XY+2X+3Y)-(3XY+2Y-2X)-(X+4Y+XY)的值急! 若x-y=4,xy=1,则(2x+y-2xy)-(3x+2y+xy)-(4xy+3y-5x)=