来自刘正东的问题
一、(1)(1/a+1/b)²÷(1/a²-1/b²);(2)(x/x+y+2y/x+y)·xy/x+2y÷(1/x+1/y);(3)(a+b/a-b)²·2a-2b/3a+3b-a²/a²-b²÷a/b;
一、
(1)(1/a+1/b)²÷(1/a²-1/b²);
(2)(x/x+y+2y/x+y)·xy/x+2y÷(1/x+1/y);
(3)(a+b/a-b)²·2a-2b/3a+3b-a²/a²-b²÷a/b;

