Seventh grade textbook of binary linear equations solution - elimination, help to solve a few mathematical problems, urgent! Using our seventh grade solution ah, to process 1. Rewrite the following equation into the form of Y expressed by an expression containing X: (1) (2) one quarter x + seven quarters y = 2; （3）5x-3y=x=2y; (4) 2(3y-3)=6x+4

Seventh grade textbook of binary linear equations solution - elimination, help to solve a few mathematical problems, urgent! Using our seventh grade solution ah, to process 1. Rewrite the following equation into the form of Y expressed by an expression containing X: (1) (2) one quarter x + seven quarters y = 2; （3）5x-3y=x=2y; (4) 2(3y-3)=6x+4

1.y=1/2-3x
2.y=8/7-1/7x
3.y=4/5x
4.y=x+3/5

The solution of the system of bivariate linear equations Who taught me? Let's first say that the substitution method is binary

1) 1. Select an equation with simple coefficients from the equation system, and express one unknown number in the equation with another unknown number. 2. Replace the equation obtained in 1. Into another equation, and eliminate an unknown number. 3. Solve the equation of one variable with a degree, and get the value of an unknown number. 4

A seventh grade student accidentally knocked over the ink bottle when doing his homework, so that only the following words could be seen in an application question: "the distance between a and B is 40km, the speed of motorcycle is 45km / h, and the speed of truck is 35km / h." Please complete the problem and solve the equation

Can add: the car and motorcycle set out from the two places at the same time, go opposite each other, and meet in a few hours
Let x hours meet, according to the meaning of the title: 45x + 35x = 40,
The solution is x = 1
2．
A: 1
Two hours to meet

Grade seven (Part Two) application problems of binary linear equations 1. There is a certain amount of water flowing into a reservoir continuously. According to the current discharge amount, the water in the reservoir can be used for 80 days, but it has been increasing recently, and the inflow has decreased by 20%. According to the current discharge amount, the water can only be used for 60 days? 2. After a worker completes half of the quota with old tools, he uses new tools to complete the quota in only 2 hours; if one third of the quota is completed with the old tools, and the rest is done with new tools, then all the quotas can be completed in 11 / 6 hours. How long does it take for the worker to process the quota separately with different tools?

1. There is a certain amount of water flowing into a certain reservoir. According to the current discharge amount, the water in the reservoir can be used for 80 days, but recently it has been increasing day by day, and the inflow volume has decreased by 20%. According to the current discharge amount, the water can only be used for 60 days

Bivariate quadratic equation A and B run on a 400m long circular track. If they run in the same direction, they will meet each other every 6 minutes and 40 seconds. If they run in the opposite direction, they will meet once every 1 minute and 20 seconds. Suppose that a runs faster than B. how many meters do they run per minute?

Let a run x meters per minute and B run y meters per minute
(x-y)(6+ 2/3)=400
(x+y)(1 +1/3)=400
That is, X-Y = 60
x+y=300
The joint solution is as follows:
x=180,y=120

A solution of a quadratic equation with two variables Group fares are as follows: More than 1-50 51-100 100 ticket buyers How much is it per person Today, there are two tour groups of AB2. The two groups buy tickets separately. The two groups add up to 1314 yuan. If they are combined into a team, it will cost 1008 yuan. How many people are there in these two groups

2. If both groups A and B have more than 50 people, they should buy 112 × 11 = 1232 yuan, which is less than 1314 yuan, which means that there are 1-50 people in a group and 51-100 people in a group. 3. Suppose that x people in group A are less than 50, and Y people in group B are 51-100 people: 13X + 11y = 1314,13x + 11 (112-x) = 1314

A mathematical problem of 2-yuan first degree equation in junior high school There are several good friends who call each other on New Year's Eve to greet each other. Every two friends talk to each other once, a total of 10 times. How many of these friends are there?

This should be a quadratic equation of one variable
There are x people
X（X-1）/2=10
X1 = 5, X2 = - 4
A: there are five

Seven years old mathematics problem uses 2 yuan 1 degree equation A railway bridge is 1000 meters long. A train passes through the bridge. It takes 1 minute for the train to cross the bridge completely. The time for the whole train to be completely on the bridge is 40 seconds. How many meters are the train speed and vehicle length?

Let: length x m, velocity v m / s
(x+1000)=60v
(1000-x)=40v
2000=100v
v=20
x=200
Answer: the length is 200m and the speed is 20m / s

Solving a mathematical problem of the first degree equation with two variables There is a section of uphill road and a section of flat road from point a to point B. if the uphill road is kept at 3km / h, the level road is 4km / h and the downhill is 5km / h, then it will take 54 minutes from point a to point B and 42 minutes from point B to place A. what is the whole journey from point a to point B?

From a to B, uphill x, level y,
So from B to a, downhill x, level y,
X/3+Y/4=54/60
X/5+Y/4=42/60
X = 1.5, y = 1.6
So the whole course = 3.1

3x+y+17=0 5y-2x+17=0 Using substitution elimination method or substitution addition and subtraction method

3x + y + 17 = 0 times 2
5y-2x + 17 = 0 times 3
X-5 can be eliminated
If we take y into any equation, we can get x = 4