A. B is any rational number, try to compare the size of a + B and a-b

A. B is any rational number, try to compare the size of a + B and a-b

When b > 0, a + b > a-b
When B = 0, a + B = a-b
When B

a. If B is a rational number, and a is greater than 0, B is less than 0, and a is less than | B |, then the size relationship of a, B, - A, - B is

a>0,b

Conclusion: when a and B are rational numbers, the size relationship between | a | + | B | and | a + B |
induce:
When a and B are rational numbers, the size relationship between | a | + | B | and | a + B |
And find the value range of X when | x | + 5 = | x + 5 |

When a and B are both positive numbers or negative numbers or one of them is 0, they are equal
a. B is not equal to 0, one is a positive number, the other is a negative number, the sum of absolute values of a and B is greater than the absolute value of their sum
X should be greater than or equal to 0

The corresponding point of rational number ABC on the number axis is shown in the figure to find the value of a-b-c-b-c
_ c_ b_ 0____ a

Boss, no picture!
Suppose A-B, B-C and C are all positive numbers, then the final result is a-2b. If B is at the origin, the answer is a. if a = 2B, the answer is 0

Find the volume of the following cylinder: bottom radius 5cm,

Bottom area = 3.14 × 5 & # 178; = 78.5 square centimeter
Volume = 78.5 × 2 = 157 CC
Comprehensive:
3.14×5²×2
=78.5×2
=157 (CC)

What does WD mean in traverse triangulation adjustment calculation? How to calculate it?

Closed conductor:
Principle of name representation
(conductor length) d total measured side length
(sum of angles) the sum of the measured left angles
(angle closure) the number of seconds of the sum of the measured left angles
The sum of the coordinate increments calculated by (coordinate closed sum difference) FX △ x
The sum of the coordinate increments calculated by FY △ y
(distance closure error) f FX square plus FY square open root sign
(traverse accuracy) K F / D (1 △ f × d)
Bonding conductor:
Principle of name representation
(conductor length) d total measured side length
(sum of angles) the sum of the measured left angles
(angle closure error) the calculated end azimuth of F β minus the theoretical end azimuth
(coordinate closed sum difference) FX △ x total minus (end x minus start x)
FY △ y total minus (end y minus start y)
(distance closure error) f FX square + FY square root opening sign
(traverse accuracy) K F / D (1 △ f × d)
Coordinate increment calculation:
△x12=D12×cosa12
△y12=D12×sina12
D: Measure the distance between two points
a: Measure the azimuth between two points
Approximate adjustment method: ① divide the angle closure error by the number of stations: F β △ n (n means the number of stations) = ∩ (angle mean), and then add the angle mean to the measured right corner
② The distance closure error is obtained by adding the root of FX square and FY square. The distance mean is obtained by dividing the distance closure error by the number of observed side lengths, and then the distance mean is added to each measured side length
③ Starting from the starting point, the coordinate increment is calculated by the formula △ X12 = D12 × cosa12, △ Y12 = D12 × sina12. The adjusted coordinates are obtained by adding the coordinate increment to the coordinates of the previous station

In the experiment of "measuring the electric power of small bulb", the power supply voltage is constant 3V, and the rated voltage of small bulb is 2.5V
After closing the switch, it is found that the small bulb is not on, the pointer of the ammeter is deflected, and the voltage indication is 0

The small bulb is short circuited

What is the difference between 1p + N and 2p leakage protection switch? By the way, is there 2p + n leakage protection switch? If so, what is the structure?

The leakage protection principle of 1p + N and 2p leakage protection switch is the same. They both detect the current difference between two poles. When the difference reaches the predetermined value, the switch will act. The difference is that both poles of 2p have overload and short circuit protection functions, while only one pole of 1p has
There is no 2p + n residual current circuit breaker. Have you ever seen 2p + n equipment? No

A kind of assorted sugar is made of milk sugar and fruit sugar according to the ratio of 3:5. How many kilos of fruit sugar is needed to prepare 240 kilos of assorted sugar?
For a triangle, the ratio of the three internal angles is 1:2:3. How many degrees are the three angles?
The ratio of pear trees to peach trees in the orchard is 3:5. It is known that pear trees are 84 lessons less than peach trees. How many pear trees and peach trees are there in this orchard?
A kind of liquid medicine is made of powder and water in the ratio of 1:100. How many kilos of powder is needed to prepare 8080 kilos of liquid medicine?
A 96cm long wire is made into a rectangular frame. The ratio of length, width and height of the rectangle is 5:4:3. What is the volume of the rectangle?
An express train and a local train depart from the two places at the same time. They meet three hours later. When they meet, the distance ratio of the two trains is 7:5, and the distance between the two places is 360 kilometers. How many kilometers do the express train and the local train travel per hour?

240 △ 8 × 5 = 150 kg 180 △ 6 = 30 ° 30 × 2 = 60 ° 30 × 3 = 90 ° 84 △ 5-3 = 42 42 × 3 = 126 trees 42 × 5 = 210 trees 8080 △ 101 = 80 kg 96 △ 12 = 8 × 5 = 40 8 × 4 = 32 8 × 3 = 24 40 × 32 × 24 = 30720 cubic cm 360 △ 12 = 30 km 30 × 7 △ 3 = 70 km 30 × 5 ^

Point P (8,1) bisects a string of hyperbola x2-4y2 = 4, then the linear equation of the string is______ ．

Let a (x1, Y1), B (X2, Y2), B (X2, Y2) be the two ends of the string respectively, and the midpoint of ∵ AB be p (8,1), ∵ X1 + x2 = 16, Y1 + y2 = 2. Substituting a (x1, Y1), B (X2, Y2) into hyperbola x2-4y2 = 4, we get x12-4y12 = 4x22-4y22 = 4, ∵ (x1 + x2) (x1-x2) - 4 (y1-y2) (Y1 + Y2) = 0