(2) parabola? "Parabolic triangle" is an isosceles right triangle, [source: Z.xx.k.Com]

The vertex of a parabola? Satisfied.

∴? .

(3) existence.

As shown in the figure, do delta? Where's Delta? About origin? Central symmetry,

Then quadrilateral? For parallel four? Edge shape.

What time? When, parallelogram? It is rectangular.

Again? ,

∴△? This is an equilateral triangle.

Work? What are feet? .

∴? .

∴? .

∴? .

∴? ,? .

∴? ,? .

Set a little? A three-point parabola? , then

Solve it, have to?

∴ What is the expression of parabola? .

25. Solution: (1) As shown in figure 1, square? Just what you want.

(2) Set a square? What is the side length of? .

∵△? Is a regular triangle,

∴? .

∴? .

∴? , that is? No denominator is right. Also correct)

(3) As shown in Figure ②, connect? And then what? . ?

Set a square? Square? What is the side length of? ,

What is the total area of them? And then what? ,? .

∴? .

∴? .

Extension? Turn it in At this point? And then what? .

Are you online? Yes,? .

∵? , that is? .

I) When? When was that? What time? Minimum.

∴? .

Ii) When? The longest time? Maximum value.

Immediately? Maximum sum? Minimum hour? Maximum value.

∵? , known by (2),? .

∴? .

∴? .

[Source: Subject Network]