X = I1 + + + I2% I3 why 30? Dizzy, beginner, I don't understand i1=10,i2=20,i3=30 In addition, why is I2 -- * + + I3 620?

--Precedence over + +*
You can see it better with a bracket
(i2--)*(++i3)
The result of (+ +) I3 is that I3 = I3 + 1 is performed first, and then I3 is returned, so the return value is 31
The result of (I2 --) is to return I2 first and then operate I2 = I2 - 1, so the return value is 20
20 * 31 = 620

As shown in the figure, the three bulbs are the same, and the indication numbers of the three ammeters A1, A2 and A3 are I1, I2 and I3 respectively after power on, then the relationship between the three current indication numbers is ()
A. I1=I2+I3B. I1＞I2＞I3C. I1=I2=I3D. I1＜I2＜I3

It can be seen from the figure that three bulbs are connected in parallel, A1 is on the main road, measuring the sum of the currents through the three lamps; A2 is measuring the sum of the currents through the lamps L2 and L3; A3 is measuring the current of the lamp L3; therefore, it can be seen that the three current representations are: I1 > I2 > I3

There are three resistors, R1 = 2 Ω, R2 = 3 Ω, R3 = 4 Ω. If they are connected in parallel, what is the current I1: I2: I3 passing through them?

In parallel circuit, the voltage of each branch is equal, U1 = U2 = U3
According to Ohm's law, i1r1 = i2r2 = i3r3
That is, I1: I2: I3 = reciprocal ratio of resistance 1 / 2: 1 / 3: 1 / 4 = 6:4:3

What is 1 + 2 + 3... + 49 + 50 + 49 + 48 +... + 3 + 2 + 1

99 items in total
The sum of the first 49 and the last 49 (1 + 49) (2 + 48) (48 + 2) (49 + 1) is 50
So the sum of 99 terms equals 49 50 plus 50 equals 50 * 50 = 2500

Using Kirchhoff's law to find the potential of point a in the circuit
As shown in the picture!

A middle school is going to organize ninth grade teachers and students to have a graduation party in Shaoshan
A middle school is going to organize ninth grade teachers and students to have a graduation party in Shaoshan
Mr. Li: Ping'an passenger transport company has two types of buses with 60 seats and 45 seats to rent. The daily rent of a 60 seat bus is 200 yuan more than that of a 45 seat bus
Xiao Fang: the teachers and students of grade eight of our school rented four 60 seat and two 45 seat buses to Shaoshan yesterday. The total rent for a day was 5000 yuan
Xiao Ming: five 60 seat and one 45 seat buses are just full
According to the above dialogue,
(1) How much is the daily rental of 60 seat and 45 seat passenger cars of Ping An passenger transport company?
(2) According to Xiao Ming's car rental plan, how much does it cost to rent a car in the company for one day?

1.6x+800=5000
x=700
60 seats: 900 40 seats: 700
2.900×5+700×1=5200

1-2+3-4+5-6+… +99-100!
calculation:
1）1-2+3-4+5-6+… +99-100；
2）1-2+3-4+5-6+… +99-100+101；
3）1-2+3-4+5-6+… +(- 1) ^ n + 1 N (n is a positive integer)

1-2 = - 1,3-4 = - 1,5-6 = - 1.99-100 = - 1, a total of 50 - 1, - 50-50 + 101 = 51N = 100, there are 50 - 1, so there are n / 2 - 1 and 1, equal to - N / 2 + 1 +(- 1) * n + 1 (n is a positive even number) "anyway, it's about this

What is the principle of vector composition?
Please tell me more about it
I didn't ask about a specific vector

Principle of vector composition: parallelogram principle

The length of the train is l, and the length of the railway bridge is also L. the train accelerates uniformly along the straight track to cross the bridge. The speed of the head of the train passing through the head of the bridge is V1, and the speed of the head of the train passing through the tail of the bridge is v2. Then the speed of the tail of the train passing through the tail of the bridge is ()
A. v2B. 2v2-v1C. v12+v222D. 2v22−v12

According to the velocity displacement formula of the process from the front of the vehicle to the front of the vehicle to the rear of the vehicle, V22 − V12 = 2Al; according to the velocity displacement formula of the process from the front of the vehicle to the rear of the vehicle, V32 − V12 = 2A · 2L, V3 = 2v22 − V12 is obtained

lim（cosx/x）=?x=0

Infinity

X = I1 + + + I2% I3 why 30? Dizzy, beginner, I don't understand i1=10,i2=20,i3=30 In addition, why is I2 -- * + + I3 620?