已知x+y分之x-y=2 求x+y分之3x-3y 减x-y分之2(x+y)的值

x+y分之x-y=2 求x+y分之3x-3y 减x-y分之2(x+y)的值
x+y分之x-y=2
x-y=2(x+y)
(x+y)分之(3x-3y)-(x-y)分之2(x+y)的值
x+y分之3x-3y
=(x+y)分之3(x-y)
=(x+y)分之6(x-y)
=6
-x-y分之2(x+y)
=-(x+y)分之2(x+y)
=-2
所以
(x+y)分之(3x-3y)-(x-y)分之2(x+y)
=6-2
=4