1. There is a group of numbers arranged according to a certain rule. The order is 2, - 5,9, - 14,20, x, 35 Can you find the value of X? What's the value of X? 2. An ant crawls on a straight line of a chessboard, and the right is the positive direction. For the first time, it climbs one unit to the right from point a, for the second time, it climbs two units to the left to point B, and for the third time, it climbs three units to the right to point C In this way, it has been climbing 20 times to A. point. Given that A. point represents - 18, what number does a point represent? 3. Given that the number represented by point a is - 27 and point B is - 15 on the number axis, find the distance between two points ab To solve this problem, several students put forward the following calculation schemes: A: The larger number minus the smaller number, that is - 15 - (- 27) = 12 B: Subtract the larger number from the smaller number, i.e. - 27 - (- 15) = - 12 C: The absolute value of the difference between the preceding number and the following number, that is | - 27 - (- 15) | = 12 D: The absolute value of the difference between the latter and the former, that is | - 15 - (- 27) | = 12 E: Draw the number axis, actually count the number, that is (here is the number axis), the distance is 12 Which plan do you think is not correct, and explain the reason. Can you think of other plans? What else do you think you should pay attention to the distance between the two points of the ball?

1. There is a group of numbers arranged according to a certain rule. The order is 2, - 5,9, - 14,20, x, 35 Can you find the value of X? What's the value of X? 2. An ant crawls on a straight line of a chessboard, and the right is the positive direction. For the first time, it climbs one unit to the right from point a, for the second time, it climbs two units to the left to point B, and for the third time, it climbs three units to the right to point C In this way, it has been climbing 20 times to A. point. Given that A. point represents - 18, what number does a point represent? 3. Given that the number represented by point a is - 27 and point B is - 15 on the number axis, find the distance between two points ab To solve this problem, several students put forward the following calculation schemes: A: The larger number minus the smaller number, that is - 15 - (- 27) = 12 B: Subtract the larger number from the smaller number, i.e. - 27 - (- 15) = - 12 C: The absolute value of the difference between the preceding number and the following number, that is | - 27 - (- 15) | = 12 D: The absolute value of the difference between the latter and the former, that is | - 15 - (- 27) | = 12 E: Draw the number axis, actually count the number, that is (here is the number axis), the distance is 12 Which plan do you think is not correct, and explain the reason. Can you think of other plans? What else do you think you should pay attention to the distance between the two points of the ball?

1 find the law: 5-2 = 3,9-5 = 4,14-9 = 5,20-14 = 6, then: x-20 = 7,7 + 20 = 27. Because +, - law is equal to +, -, +, -, -,. So: x = - 27.2 is related to the addition and subtraction of rational numbers