若4x-3y=0,则4x-5y/4x+5y的值是?

若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 若|2x-y+5|+(x+2y-4)的平方=0,则（2x-y)的三次方-（x-3y)(y-2x)的平方 若5x+3y=3x+4y=x+2y+6,则x+y=___ 若x/y=4/3 则3x+2y/2x-5y= 若4x-5y=0,则x+y分之x-y的值是 若2x-3y=0,求5x+4y/3x-2y （5x+3y)(3y-5x)-(4x-y)(4y+x)= x*x+2x+y*y-4y+5=0 x= y= 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 若x,y满足约束条件x-y+5≥0,x+y≥0,x≤3,则z=4x-y的最小值为?具体过程 若实数x,y满足x的平方+y的平方-4x-2y+5=0,则（x+y）/2x-3= 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 4x=5y (y不等于0).则有.y.y/x.x-y.y=? x+y／y=5／4,则x／y=----------------