数学领域中,有不少貌似实异的对象.对它们的运用,常出现“张冠李戴”之错.只有准确掌握它们的区别,才能无误地用好它们.现以三个结论为例,深入剖析如下.(1)存在实数x与y,使(?)=x(?)+y In the field of mathematics, there are many seemingly real objects. The use of them often appears with the mistake of “changing and wearing.” Only by accurately grasping the differences between them can we make good use of them without mistakes. Now take three conclusions as examples. In-depth analysis is as follows. (1) There are real numbers x and y, so that (?) = x (?) + y