x/20+y/15=40 y/12+x/6=75,解方程,

12x+20y=20x+15y 已知x+y+y=20,x+y=15求x.y X+Y=40,(X*Y)/(X+Y)=7.5 (12-x)*y+x*2=26 (15-x)*y+y*2=35(12-x)*y+x*2=26 (15-x)*y+y*2=35 解方程组 x+2y=1.5,12(x+y)+15y=20 x/20+y/15=40 y/12+x/6=75,解方程, x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 (x*x+y*y)(x*x+y*y)-(x*x+y*y)=12 求x*x+y*y等于多少 化简 x / y(x+y) - y / x(x+y) = 12x+20y=20x+12y 40X+30Y=2200 X>20 Y 解方程 {x+y=20 x-y=12 x+y=18 x/12 +y/8 =20 x+y=180 x/12+y/8=20x+y=180x/12+y/8=20 x^2+xy=12,xy+y^2=15,求(x+y)^2-(x+y)(x-y) x.y都是自然数,且x(x-u)-y(y-x)+12,求x.y得值快1且x(x-y)-y(y-x)=12 x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 20(x+y)=12(y+z)=15(z+x),且xyz不等于零,求x:y:z=