4x+5y=34 5x+4y=65 则x+y= x-y=多少求

x+y／y=5／4,则x／y=---------------- 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 5x-4y(y-x)=? y=|-x.x+4x+5| （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 4x=5y (y不等于0).则有.y.y/x.x-y.y=? 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 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：4x = 5y,求(x+y) ：y 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 x-y+5x-4x= ?x-y+5x-4x= ? 4X+5Y=34 5X+4Y 若(X×X+Y×Y)(X×X+Y×Y-5)=36,则X×X+Y×Y＝ 已知5x=4y,则x:y=():()