Negative number is less than 0.

(1)0 is neither positive nor negative. 0 is the boundary between positive and negative numbers.

(2) The meaning of 0 is not only "no", but also other meaning. Going to 0℃ is a certain temperature, and 0 meters above sea level is the average height of sea level.

Matters needing attention

1. The "+"in front of a positive number can be written or omitted, and the "-"in front of a negative number cannot be omitted.

2. To judge whether a number is negative, one is to see whether there is a negative sign in front of it, and the other is to see whether the number behind the negative sign is positive.

3.0 is the smallest natural number, and 0 is both positive and even.

Use positive numbers and negative numbers to represent quantities with opposite meanings.

1. quantities with opposite meanings

(The opposite meaning is simply the antonym of Chinese)

We can use positive numbers and negative numbers to represent some quantities with opposite meanings. When positive numbers and negative numbers are used to represent quantities with opposite meanings, which meaning is positive can be chosen at will. When a quantity is known to be represented by a positive number, the quantity with opposite meaning is represented by a negative number; or vice versa, Dallas to the auditorium

2. Expression of quantities with opposite meanings

Words describing a pair of quantities with opposite meanings are generally antonyms, such as rising and falling, increasing and decreasing, profit and loss, income and expenditure. In addition, there should be a specific number. As for which one is positive, it usually depends on the idioms in life or we stipulate that one of them is positive and the other is negative.

3. Interpretation of "the quantity with opposite meaning"

1.( 1) must be the same quantity. For example, saving 3 tons of gasoline and wasting 1 ton of water are not quantities with opposite meanings;

(2) The meanings expressed should be completely opposite, not just different. For example, east and south are not quantities with opposite meanings.

2. Increase, increase, profit and income are recorded as positive, while decrease, decrease, loss and expenditure are recorded as negative.

Question type 1

Example 1? The following statement is true ()

(1) Numbers without "-"are all positive numbers; (2) If A is positive, then -a must be negative; (3) Numbers without "+"are all negative numbers; (4) There is no number that is neither positive nor negative; (5) Non-positive numbers are negative numbers.

A.0 B. 1？ C.2？ D.3

(DuDu, don't look down)

Analysis: 1. Incorrect, the root of all evil 0 is neither positive nor negative.

2. correct. The plus sign "-"before a positive number must be a negative number.

3. No, the root of all evil 0 has no positive sign, but it is not negative either.

4. No, the root of all evil is 0. It is neither positive nor negative.

5. No, 0 is not positive, but not negative.

Let's call it a day. Continue to sort out the examples tomorrow.

Come on! ! ! ! ! ! !