① Like 0, 1, 2, 3, 4, 5, 6, ...

natural number

. Numbers like -3, -2,-1, 0, 1, 2, 3, ... are all integers.

② We only study multiples and factors within the range of natural numbers (except zero).

The multiple of 2 is called even number, and the multiple of 2 is not called odd number.

④ Features of multiples of 3: The sum of numbers on each digit is multiples of 3. 9 is the same.

⑤ A number has only two factors, 1 and itself. This number is called.

prime number

. A number has other factors besides 1 and itself. This number is called sum number.

6. 1 is neither prime nor sum.

⑦2 is the only even prime.

The smallest prime number is 2 and the smallest sum number is 4.

Pet-name ruby startup state is not the first time, the startup state of the object, must be clear, to judge accurately.

Attending walk between two points, walk odd times and then return to the starting point.

Second: the area of the graph (1)

(1) The areas of two graphs with the same shape and size are not necessarily equal; Two graphs with the same area may have different shapes.

②

axial symmetric figure

(or a graph composed of the same parts) can be evenly divided.

(3) Draw the bottom of the specified length first, then the height of the specified length, and then draw other sides, which is easier to draw.

④

parallelogram

Area: bottom times height (S=ah).

⑤ The area of triangle is half that of parallelogram with equal base and equal height. (S=ah÷2)

⑥ parallelogram = upper bottom+lower bottom of the original trapezoid.

Height of parallelogram = height of original trapezoid.

⑦ Trapezoidal area = (upper bottom+lower bottom) × height ÷2

[S=h(a+b)÷2]