-2(x-y)与3(x-y)是同项式吗?

-2(x-y)与3(x-y)是同项式吗?为什么?4(a+b)和-4(a+b)呢?如果是同类项，他们的和是什么 (麻烦详讲)在线等追加

(2x+y)(2x-y)-(3x-2y)(x+y)-y(2x-y) (x-2y)^2+(x-y)(x-2y)-2(x-3y)(x-y) X与Y是无理数，X+Y=2，X，Y各等于几？ x^2+3(x+y)+3-y^2+(x-y) (X-3y)(x+3y)-(x-3y)^2 3X(X-Y)+2Y(X-Y) 3(x+y)(x-y)+4(x-y)^2=? 3(X+Y)-2(X-Y)+2 已知x,y∈R是2^x+3^y≤2^-y+3^-x,则x,y满足 3(x+y)-2(x-y)=9 5(x+y)+2(x-y)=-1