Or just or

Like x? = 1，x- 1=0。

Then x can only be 1.

This is the intersection of two sets {- 1, 1} and {1}.

And what about x? = 1 or x- 1 = 0x = 1.

This is the union of two sets {- 1, 1} and {1}.

In layman's terms, that's it

You can go to the encyclopedia and read the professional explanation yourself.

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A=b=0 is actually a=0 and b=0, that is, both a and b are equal to 0.

Negative expressions A and B are not both equal to 0, or a=0 or b=0.