The meaning of the three formulas in the first question on page 64 of PEP

The meaning of the three formulas in the first question on page 64 of PEP

The diameter of a flower bed is 20 meters. How many meters is its perimeter?
3.14 times 20 = 62.5 (perimeter C = π d = 3.14 * 20 = 62.5m)
There should be some questions in the latter two forms

64 = 65 square area
The area of the block diagram is calculated as 64

Notice the line that cuts. It doesn't go through the corners of every small square
Take a closer look. Where did it happen
Pay attention to the dislocation of a and B joints after 65
I can't spell it
If you can't see it, try to find a piece of paper
I'll be out in a minute

It's the definition of "domain". It's not the interval of "domain"!
I'm sorry. dial the wrong number. It's neighborhood. Please see clearly again. Don't mean interval. To define! The so-called definition, and do not encyclopedia + copy. I'll read the encyclopedia, too.

You've got the wrong number. It's "neighborhood". It's an introduction to the definition of limit in higher mathematics. It's an emerging concept. Neighborhood refers to the area with a certain point as the diameter and a certain size as the radius. I remember that. Of course, you can also find it in higher mathematics. It's somewhere in the previous chapters

Why is the square 64 and the rectangle 65?
An 8cm x 8cm square is divided into two rectangles of 5cm x 8cm and 3cm x 8cm, and then the 5cm x 8cm rectangle is divided into two trapezoids of the same size (upper side = 5cm, lower side = 3cm, height = 5cm), Then divide the 3x8 rectangle into two triangles of the same size (bottom = 8cm, bottom = 3cm). Finally, combine two trapezoids and two triangles to form two large triangles (the 3cm side of trapezoid is connected with the 3cm side of triangle), and then form a 5cm x 13cm rectangle. What's the reason?

The angle of the bottom edge of the trapezoid is not equal to the angle of the triangle adjacent to the 3cm edge, so when combined, there is a gap. That is the difference of 1 square centimeter