定义一种新运算:a▲b=2a-b. (1)直接写出b▲a的结果; (2)计算:[(x-2y)▲(x+y)]▲3y.

问题描述:

定义一种新运算:a▲b=2a-b.
(1)直接写出b▲a的结果;
(2)计算:[(x-2y)▲(x+y)]▲3y.

(1)原式=2b-a;
(2)原式=[2(x-2y)-(x+y)]▲3y
=(x-5y)▲3y
=2(x-5y)-3y
=2x-13y.