The eighth grade mathematics book of Beijing Normal University Edition?

(1) Let's rent x cars with 45 seats. According to the meaning of the question 45x = 60 (X-2) + 30, the solution is x = 6, so there are 270 students with 45 * 6
(2) A car with 45 seats and a + 1 car with 60 seats will be rented
45a+60(a+1)≥270
250a+300（a+1）

What's the answer to questions 1, 2 and 4 of the general review of mathematics in Volume 2 of Grade 8?
Not to copy, but to solve my questions!
1. Solve the following inequalities and express their solution sets on the number axis respectively
(1) 3x-2x less than 5 (2) X-6 greater than 2x (3) x / 2 greater than X / 3 (4) 2x-7 greater than 5-2x (5) 1-3x / 2 greater than 1-2x
(6) X-1 / 2 (4x-1) less than or equal to 2 (7) X-1 / 2 + 1 less than or equal to X / 4 (8) 0.01x-1 less than or equal to 0.02
It's the dead B who won't swear
It's better to write down the process

(1) X-6 (3) X>0 (4)X>3 (5)X>1
(6) X less than or equal to - 3 / 2 (7) x less than or equal to - 2 / 3
(8) X is less than or equal to 102
Note: when drawing the number axis, is the point hollow or solid

English words in unit 4 of PEP English eighth grade volume 1
Be accurate

Take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway, take the subway

How many jin is 100 gram red mung bean equal to?

2 liang

When a = - 2, - a2-2a + 1= When 2A + 3B = 1, 8-4a-6b= ．

When a = - 2, - a2-2a + 1 = - 4 + 4 + 1 = 1, when 2A + 3B = 1, 8-4a-6b = 8-2 (2a + 3b) = 8-2 = 6

Some questions about the electric power of physics in grade two of junior high school,
1. The bulb marked with 220 V and 40 W is connected to the 110 V circuit, and its actual power is___ W
2. If the resistance of two lamps L1 and L2 in parallel in the circuit is small, and the resistance of L2 is large, the lamp will be overactive_ The electric current is high, the electric light is low_ High power electric lamp_ It's brighter
3. What is the power consumption of a 4-amp resistor connected to an 8-v circuit W. A 220 V 100 W electric lamp works normally for 5 hours Kilowatt hour
4. If the voltage ratio of the two resistors is 3:1, the current ratio is 1:2, and the power on time ratio is 3:2, then the current through the resistance ratio is 1:2_ The ratio of their electric power is_
5. If L1 and L2 are connected in parallel in the circuit, and R1: R2 = 2:1, the ratio of current passing through the two lamps is 0_ What is the ratio of electricity consumed in the same period of time
6. There is a small bulb marked 8V 2W, which must be connected to 12V power supply_ Connect a resistor for Ohm resistance can make the small bulb light normally. At this time, the electric power of the trumpet on this resistance is_ W

1. R = u / (P / U) = 1210 Ω, p '= u · U / r = 10w2. The voltage at both ends of parallel circuit is equal, U1 = u2i = u / R R1 ＜ R2 I1 ＞ i2p = u · U / R R1 ＜ R2 P1 ＞ P2. The lamp with high power is brighter. 3. It seems that there is no 4A resistance ~ 100W = 0.1kww = P · t = 0.1kw · 5h = 0.5KW · H4. R = u / I U1 / U2 = 3:1

Vector projection problem
Projection of a = i-2j + 3K on y-axis
Projection of a = i-2j + 3K on vector b = I + k
Dizzy

The projection in which direction is multiplied by the unit vector in which direction
Projection of a = i-2j + 3K on y-axis
a*j=(i-2j+3k)*j=i*j-2j*j+3k*i=0+(-2)+0=-2
The unit vector on vector B is: e = B / | B | = (radical 2 / 2) I + (radical 2 / 2) K
Projection of a = i-2j + 3K on vector b = I + k
a*e
=(i-2j + 3K) * ((radical 2 / 2) I + (radical 2 / 2) k)
=(radical 2 / 2) + 0 + 3 (radical 2 / 2)
=2 root 2

The football kicked by the player along the grass, rolling more and more slowly on the grass, and finally stop. From the player playing football to the process of football stopping on the grass ()
A. No force does work on football. B. gravity does work on football
C. The energy consumed by athletes is converted into kinetic energy D. the energy consumed by athletes is converted into heat energy

The answer is d
The work done by the player to the ball when playing football is transformed into the kinetic energy of the football and the energy consumed by the player
Football on the grass, finally stop, kinetic energy into internal energy (heat)
In the whole process, the energy consumed by athletes is transformed into heat energy

The acceleration of the ball when the ball springs and rebounds

There is a special position where the spring force is equal to the gravity. Let's set it as point o
When the ball falls from a certain height, the acceleration is g before contacting the spring, and the velocity increases
When the spring is just touched, the elastic force is less than gravity, so the resultant force is downward and the acceleration is downward. The resultant force is gravity minus the elastic force. The elastic force gradually increases and the resultant force decreases, so the acceleration decreases and the velocity increases, which is above the o point
When it reaches o point, the acceleration is 0 and the velocity reaches the maximum
From o point to the lowest point, the resultant force increases, the acceleration increases, and the velocity gradually decreases to 0
When returning from the lowest point to o point, the acceleration becomes smaller and the velocity becomes larger
From point O to leaving the spring, the acceleration increases and the velocity decreases

Given that the frequency of Korean alternating current is 60 Hz, can you find out the period of Korean alternating current?
In 1831, Faraday's experiment finally made a breakthrough. In his experiment diary on August 29, Faraday wrote: "first, some experiments of generating electricity by magnetism, etc." Faraday's experiment was like this: there are two groups of coils a and B wound on an iron ring, as shown in Figure 2. Coil a is wound with three strands of wire, coil B is wound with two strands of wire, The two coils can be used alone or in combination. The tap of coil B is connected to a closed loop, and the two ends of coil a are connected to the battery pack. When the power is turned on, the small magnetic needle near the closed loop swings obviously; when the current is cut off, the magnetic needle swings in the opposite direction, which is very short-term, This is the famous Faraday ring experiment. This experiment is usually regarded as the discovery of electromagnetic induction phenomenon. Faraday himself called this experiment the induction of electric current. He thought that this is not his ideal phenomenon of magnetic electricity generation. He improved the experimental instrument and continued the experiment. He replaced the small magnetic needle with a string galvanometer, changed the iron ring into an iron rod and then into a hard paper tube, Faraday decided to use a magnet instead of electric current to directly reflect the reverse effect of Auster effect, which is to convert magnetism into electricity. He paralleled the eight coils wound on the cardboard tube and connected the end point to the galvanometer. He picked up a magnetic rod and suddenly inserted it into the paper tube. He saw the pointer of the galvanometer move. When he suddenly pulled out the magnetic rod, Faraday's heart was open, The pointer moved in the opposite direction again. He tried again and again. The pointer swung back and forth The ideal of turning magnetism into electricity has finally come true. This day is October 17, 1831
Faraday's experiment of winding two coils around an iron ring in 1831, at the moment of closing and opening the switch

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The eighth grade mathematics book of Beijing Normal University Edition?