5x+2y/3=3/2-2x-3y/2 2(5x+2y)/3-49=3(2x-3y)解二元一次方程组半小时内,

已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 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 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 化简:5(x-y)+2(x+y)-3(x-y) 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) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= (x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一 (2x-3y)-(5x-y) (2X-3y)-(5x-y) (2x-5y)(3x+y) (x+y)(2x-3y)=? x(x-y)2-(y-x)3 {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? 因式分解(x-2y)(x-3y)+(x-4y)(x-5y)+（x-3y)(x-5y)+(x-2y)(x-4y)