(x-y)/4+(x+y)/5=1/4 (x+y)/9-(x-y)/3=//2(x-y)/4+(x+y)/5=1/4(x+y)/9-(x-y)/3=//2

化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 5x-4y(y-x)=? (x+y)(x-y)+4(y-1) {x+y=1 ,xy=-6{x(2x-3)=0,y=x²-1{(3x+4y-3)(3x+4y+3)=0,3x+2y=5{(x-y+2)(x+y)=0,x²+y²=8{(x+y)((x+y-1)=0,(x-y)(x-y-1)=0 x+y／y=5／4,则x／y=---------------- 已知：4x = 5y,求(x+y) ：y （5x+3y)(3y-5x)-(4x-y)(4y+x)= {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 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 {3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1 3x-2y=1 4x-5y 1/5x=4y改成比例式x:y():(). (x-y)/4+(x+y)/5=1/4 (x+y)/9-(x-y)/3=//2(x-y)/4+(x+y)/5=1/4(x+y)/9-(x-y)/3=//2 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 ｛x-y=4 ｛5x-y=110 4x-y=－1 9y-x=110