1. Proposition "Two sides of an equation are multiplied by the same number, and the result is still an equation." If the result is not an equation, then both sides of the equation are not multiplied by the same number. _"

2. Write down the negative propositions of the following propositions and judge whether they are right or wrong.

Two triangles with three corresponding equilateral sides are congruent.

No proposition: two triangles corresponding to three sides are not equal.

Judgment: The original proposition is true and its negative proposition is false.

3. Judge right or wrong.

If the negative proposition of a proposition is true, then its inverse proposition must be true.

Judgment: true (because they are mutually negative propositions? )

4. Choose from necessary and sufficient conditions, necessary conditions, sufficient conditions and conditions that are neither sufficient nor necessary.

1.x 2 = 3x+4 is the "_ necessary condition _" of x=√(3x+4).

2. "Irrational number of A+5" is the "necessary and sufficient condition" for "A is irrational number"

3. "The two diagonals of a quadrilateral are equal" is a "necessary condition" for a quadrilateral to be a rectangle.