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What are the necessary and sufficient conditions for high school mathematics?
First, sufficient conditions?

1, overview?

Sufficient conditions will certainly ensure the emergence of results.

2. definition?

Where there are things, there must be things; If there is no case A but not necessarily no case B, then A is a sufficient and unnecessary condition of B, which is called sufficient condition for short. Simply put, to satisfy A, it must be B; If A is not satisfied, it is not necessarily B, then A is a sufficient condition for B..

For example:

1, a rain; The ground is wet.

2. A handful of firewood; B will produce carbon dioxide.

In an example, a is a sufficient condition for b. To be exact, A is a necessary and sufficient condition for B;

First, A will inevitably lead to B;

Second, A is not a necessary condition for B to occur.

Second, the necessary conditions?

1, overview?

If there is no situation A, there must be no situation B; If there is something, there is not necessarily something, then A is the necessary and sufficient condition of B, referred to as the necessary condition.

2. definition?

Simply put, if you don't meet A, you won't meet B; Satisfying a does not necessarily mean b, then a is a necessary condition for B.

For example:

1. Keep breathing; B people can live

2.a knows 26 letters; B can read English.

3. One has heard of Peking Opera; B can appreciate the beauty of Beijing opera.

In the example, A is a necessary condition for B, to be exact, A is a necessary but not sufficient condition for B;

First, A is a necessary condition for B to occur;

Second, A does not necessarily lead to B.