X+Y=164800*X/60+12000*Y/60=1880

x+x+x+y=60 .x-y=4 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 化简 x / y(x+y) - y / x(x+y) = y=x(x x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 x+x+x+x+y+y+y=56 3.2x+60+x=y ｛x/60+y/80=10,x/60+y/40=15、｛2x/3+3y/4=1/5,5x/6-5y/2=2、｛5/2(x+y）=1200,10/3（x+y）=1200｛4x+5y=98,5y-4x=2、｛x/3+y/4=54/60,y/4+x/5=42/60怎么解?{40-y=x-4 40-y=y-x x＋x+x－y-y＝60 y+y+y-x-x=10 那么x=? y=? X+Y=164800*X/60+12000*Y/60=1880 推倒公式:(x+y)(x*x-3x+y*y)=x*x*x+y*y*y怎么做. x+y=7 900x=1200y , 900x=1200y x+y=7 x+y=7 900x=1200y 嗷 x+x+x+y+y=6.4 y+y+y+x+x=7.1 怎么算? 二元函数f(x,y)=x+y/x-y,求f(y/x,x/y) x-y/x+y=(x-y)²/x²-y²（x≠y) （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y