1.30 times the root number 2 (to cover the table, the diagonal of the square table is the longest and the radius of the circle is at least half of the diagonal of the table).

2.A

Left plus right MINUS

add, subtract, multiply and divide

It's very clear upstairs.

3. mm-hmm . This problem

It should be -x2- 1.

Let a point on the parabola after rotation be (x, y), then the coordinate of the point before rotation is (-x, -y), and at y=x2+ 1, bring it in (this is the general method of this kind of problem, which can be handled in this way, and this problem can be drawn directly).

4. 16 or 25

1) When BC is waist, one of AC and AB must be 8.

That is to say, the equation has a root of 8, which leads to the solvable m= 16.

2) When bc is the bottom, then AB=AC, that is, the two equations are equal, discriminant =0, and the solution is m=25.

Is this ok? It should be right. Look again ~