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The definition of rational number in the first day of junior high school
Rational number can be divided into integer and fraction. Any rational number can be written in the form of fraction M / N (m, n are all integers, and N ≠ 0). Any rational number can be expressed on the number axis, including integer and fraction, In mathematics, a rational number is the ratio of an integer a to a non-zero integer B, which is usually written as a / B, so it is also called a fraction. In Greek, it is called λ ο γ ο, which originally means "rational number", It gradually becomes "rational number". Infinite non cyclic decimal is called irrational number (for example: PI). Rational number and irrational number are collectively called real number. The set of all rational numbers is expressed as Q
(1) Integers include: positive integers, 0, negative integers, collectively known as integers
(2) Scores include: positive scores and negative scores are collectively referred to as scores
(3) Decimals include: finite decimals, infinitely circular decimals. And fractions are also called decimals, because the fraction is reciprocal
The addition and subtraction of rational numbers; process. + 5 + (- 3.4) + (- 4.6) + (+ 6) (- 1)
=5-3.4-4.6+6-1
=5+6-(3.4+4.6)-1
=11-8-1
=2
=5-3.4-4.6+6-1=5+6-(3.4+4.6+1)=11-9=2
Original formula = + 5-3.4-4.6 + 6-1
=11-9
=2
If there is any help, please take it. Thank you!
How to move two points in ABC so that the number represented by three points is the same? There are several ways to move
A= -4 B= -2 C=3
Please give me a more concise answer. Don't use complicated Chinese characters
A fixed, B left 2 units, C left 7 units, all means - 4
B does not move, a moves 2 units to the right, C moves 5 units to the left, which means - 2
C doesn't move, a moves 7 units to the right, B moves 5 units to the right, all means 3
The tortoise starts from point a and crawls at a speed of 1 unit length per second, while the rabbit comes out from point B
If the tortoise and the rabbit start to move at the same time for 3 seconds, then the rabbit is at - 2 on the number axis, and the tortoise is at 1 on the number axis. (1) when they move for 3 seconds, what are the numbers corresponding to the positions of the tortoise and the rabbit when they are closest to each other? And find out the nearest distance between the tortoise and the rabbit
(2) When they are farthest apart after 3 seconds of movement, what are the corresponding numbers of the positions of the tortoise and the rabbit, and find out the farthest distance between the tortoise and the rabbit
(1) The tortoise starts from point a and crawls at the speed of 1 unit length per second, while the rabbit starts from point B and moves at the speed of 3 units length per second. We think that their movement direction is in the positive direction (right). Because the speed of the rabbit is faster than that of the tortoise, as time goes on, their distance will be closer and closer, At first, the distance between them is 2 - (- 3) = 5. The rabbit is 2 units faster than the tortoise in length per second, 5 △ 2 = 2.5, which means that the distance between them is the closest at 2.5 seconds. At this time, the number of the position of the rabbit and the tortoise is 2 + 1 × 2.5 = - 3 + 3 × 2.5 = 4.5
(2) The farthest distance is of course the original position (tortoise: 2) (rabbit: - 3)
(this topic doesn't explain the specific direction of the movement. We can also consider the situation when they are in the opposite direction, but that's a bit wordy.)
Corresponding number of 42 points
It is known that the number corresponding to point a on the number axis is 1, and the number corresponding to point B is - 2. The tortoise starts from point a and crawls at the speed of 1 unit length per second, which is small
It is known that the number corresponding to point a on the number axis is 1, and the number corresponding to point B is - 2,
The little white rabbit starts from point B and moves at a speed of 3 units per second. If they start to move for 3 seconds at the same time, please answer (1) when they are farthest apart, what are the corresponding numbers of the positions of the tortoise and the little white rabbit? (2) when they are nearest, what are the corresponding numbers of the positions of the tortoise and the little white rabbit?
① 4 and - 11, ② - 2 and 7
It is known that the number corresponding to point a on the number axis is 2, and the number corresponding to point B is - 3. The tortoise starts from point a and crawls at the speed of 1 unit length per second, and the rabbit comes out from point B
If they start at the same time and move on the number axis for 3S, please answer: (1) when they are closest, what are the corresponding numbers of the positions of the tortoise and the rabbit? (2) when they are farthest, what are the corresponding numbers of the positions of the tortoise and the rabbit?
At the nearest time, the tortoise corresponds to 1 and the rabbit to 0; at the farthest time, the tortoise corresponds to - 1 and the rabbit to 6
It is known that the number corresponding to point a is 2, and the number corresponding to point B is - 3. The tortoise starts from point a and crawls at a speed of one unit per second
Starting from point B, they move at a speed of 3 units per second. If they start at the same time and move for 3S on the number axis, please answer: when they are closest to each other, what are the corresponding numbers of the positions of the tortoise and the rabbit? When they are farthest away, what are the corresponding numbers of the positions of the tortoise and the rabbit?
1. The closest time is when they meet. At this moment, their moving time is t = 5 / (1 + 3) = 1.25 seconds. Therefore, the position of the tortoise is 0.75, and that of the rabbit is 0.75. The farthest time is three seconds later, the position of the rabbit is 6, the position of the tortoise is - 1, and the distance is 7
On the number axis, the number corresponding to point a is - 1, and the number corresponding to point B is 1. A beetle starts from point B and crawls along the positive direction of the number axis at a speed of 4 units per second to point C, and then immediately returns to point a, which takes 4 seconds. (1) find the number corresponding to point C; (2) if the beetle returns to point a and then moves as follows: crawling 2 units to the right for the first time, crawling 4 units to the left for the second time, crawling 3 units to the left for the third time For the first time, it crawled 6 units to the right, for the fourth time, it crawled 8 units to the left (3) if the beetle returns to a and continues to crawl along the negative direction of the number axis at a speed of 4 units per second, then the other beetle B starts from point C and crawls along the negative direction of the number axis at a speed of 7 units per second. Let the point corresponding to beetle a be point E, and the point corresponding to beetle B be point F, and set points a, e, and F The numbers corresponding to a and B are Xa, Xe, XF and XB respectively. When the movement time t does not exceed 1 second, the following conclusions can be drawn: ① | XA Xe | + | Xe XF | - | XF XB | does not change; ② | XA Xe | - | Xe XF | + | XF XB | does not change; only one of the conclusions is correct, please choose the correct conclusion and find its fixed value
(1) According to the meaning of the title: 4 × 4 − 22 = 7, 7 + 1 = 8, that is, the number of points corresponding to point C is 8; (2) according to the meaning of the title: - 1 + 2 + (- 4) + 6 + (- 8) + 10 + (- 12) + 14 + (- 16) + 18 + (- 20) = - 11, that is, the number corresponding to the point where the tenth crawling stops is - 11; (3) ② | XA Xe | - | Xe XF | + | xf-xb |
If a small ant starts from point a of - 4 on the number axis and crawls to the right for 3 seconds at a speed of 2 units per second, then the number represented by point B is ()
A. 2B. -4C. 6D. -6
According to the meaning of the question, we get - 4 + 2 × 3 = - 4 + 6 = 2
The number represented by point a on the number axis is - 1. A small insect starts from point a and crawls along the number axis at the speed of 5 units per second to the back of point B,
It takes 9 seconds to return to point a, then how many unit lengths does the bug crawl to point B? What is the number represented by point B?
45 units in length, point B stands for 44
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