For example:

1. Because zero denominator is meaningless.

So a≠0

2. Because x- 1≠0, x≠- 1.

3. Because 3m+2≠0, m is not -(2/3).

4. Because x-y≠0, X ≠ Y.

5. Because 3a-b≠0. . .

Just write it yourself. . . . .

1.a is not 0.

2.x is not 1.

3.m is not -(2/3)

4.x is not equal to y.

5.a is not equal to 1/3(b)

6.x is not equal to 2

……

In short, it is meaningless to remember that the denominator is 0.