Please use a quadratic equation of two variables or a quadratic equation of three variables to solve it 1. Car a and car B, car a goes from a to B, and car B goes from B to a, and they run in opposite directions at the same time. After 1.5 hours, the two cars meet. After meeting, car a still needs 2 hours to arrive at B, and car B still needs 9 / 8 hours to arrive at a. if a and B are 210 km apart, try to find the speed of car a and car B 2. A project is completed by Party A and Party C in 6 days. The total cost of the two teams is 8700 yuan; the total cost of the two teams is 9500 yuan; the total cost of the two teams is 5500 yuan (1) How many days does it take for each team a, B and C to complete the whole project independently? (2) If it is required to complete the whole project within 15 days, which team can complete the project independently with the least cost? Please explain the reason

Please use a quadratic equation of two variables or a quadratic equation of three variables to solve it 1. Car a and car B, car a goes from a to B, and car B goes from B to a, and they run in opposite directions at the same time. After 1.5 hours, the two cars meet. After meeting, car a still needs 2 hours to arrive at B, and car B still needs 9 / 8 hours to arrive at a. if a and B are 210 km apart, try to find the speed of car a and car B 2. A project is completed by Party A and Party C in 6 days. The total cost of the two teams is 8700 yuan; the total cost of the two teams is 9500 yuan; the total cost of the two teams is 5500 yuan (1) How many days does it take for each team a, B and C to complete the whole project independently? (2) If it is required to complete the whole project within 15 days, which team can complete the project independently with the least cost? Please explain the reason

1. Set speed a as X km / h and speed B as y km / h
1.5(X+Y)=210
2X+9/8Y=210
The solution is x = 60, y = 80
A
2. Suppose that Party A completes x, B is y and C is Z of the total project every day
6（X+Y）=1
10（Y+Z）=1
5（X+Z）=2/3
The solution is: x = 1 / 10, y = 1 / 15, z = 1 / 30
Suppose a spends X Yuan, b y yuan and C Z yuan every day
6（X+Y）=8700
10（Y+Z）=9500
5（X+Z）=5500
The solution is: x = 800, y = 650, z = 300
So a single 10 * 800 = 8000 yuan
Party B: 15 * 650 = 9750 yuan
C can't finish it alone within 15 days, so I don't think about it
Answer: (1)
（2）.

The sum of a three digit number, a single digit number and a hundred digit number is equal to a ten digit number. Seven times the sum of a hundred digit number is two times larger than that of a single digit number and a ten digit number. The sum of a single digit number, a ten digit number and a hundred digit number is 14

This three digit number is x on the one digit, y on the ten digit, and z.x + Z = y on the hundred digit. ① 7z = x + y + 2x + y + Z = 14. ③ substitute ① into ③ to get y = 7. Substitute y = 7 into ① to get x + z = 7. ④ substitute ② to get 7z = x + 9. ⑤ ④ - ⑤ to get z = 2, ｜ x = 5. This three digit number is 2 × 100 + 7 × 10 + 5 = 275. Answer: this three digit number is 275

3x-5% = 58x divided by 1 / 2 = 3 / 5

3x-5% = 5
3x/4=5+1/20
3x/4=121/20
x=121/15
8x divided by 1 / 2 = 3 / 5
8x=3/5*(1/2)
x=3/10÷8
x=3/80

The side length of square a is one centimeter more than twice that of square B, and their perimeter is 24 centimeter different. What is the area of square a and square B?

If the length of side B is x, then the length of side a is 2x + 1
4*（2X+1）-4X=24
The solution is as follows
X=5
2*5+1=11
So a area = 11 * 11 = 121 square centimeters
B area = 5 * 5 = 25 cm

Speed is a physical quantity that describes how fast an object moves
Can we say that the instantaneous velocity is a physical quantity describing the speed of an object? Or the average velocity is a physical quantity describing the speed of an object?

It's really hard to answer this question. First of all, the physical meaning of speed is the physical quantity reflecting the speed of an object's movement. From this point of view, both of your above statements should be true. But when an object is moving at a variable speed, the instantaneous speed of the object is useless to us (at least in junior high school

If 2x ^ NY ^ 4 and 1 / 2m ^ 2x ^ 2Y ^ M-N are binomials of degree 6 about X and y, and the coefficients are equal, the value of M and N is the absolute value

Coefficient 2 = 1 / 2m & sup2;
m²=4
m=±2
6 times, then n + 4 = 6, n = 2
2+|m-n|=6
|m-2|=4
m=±2
So m = - 2, n = 2

Cut a circle of paper into two sectors along the radius, and the ratio of the center angle of the circle is 3:4,
Then the volume ratio of the two cones is?

The volume formula of a cone is v = bottom area * height * 1 / 3. Assuming the radius is r, then the circumference of the circle is 2 π R. if the circle is divided into seven equal parts, then the relatively small circumference of the cone is 3 / 7 * 2 π R, that is 6 / 7 π R; the relatively large circumference of the cone is 8 / 7 π R. from the circumference, we can get the relatively small radius of the cone, R small = 6 / 7

How to check the equation

Replace the value of the unknowns with the original equation, and the numbers on the left and right sides of the equation are equal

What is the absolute value x1-x2 equal to
The two real roots of the quadratic equation AX2 + BX + C = 0 are X1 and x2
Find: absolute value x1-x2
In letters,
By the way, it's not over. The second question is the third power of X1 + the third power of X2, also expressed in letters

x1+x2=-b/a
x1x2=c/a
So (x1-x2) & sup2; = (x1 + x2) & sup2; - 4x1x2
=b²/a²-4c/a
=(b²-4ac)/a²
So | x1-x2 | = √ (B & sup2; - 4ac) / | a|

The radius of the circle increases by 1 / 5, the circumference of the circle increases (), and the area of the circle increases ()

It increased by 1 / 5, increased to 6 / 5, and the similarity ratio was 6 / 5
Increased length: original length = similarity ratio
Increased area: original area = square of similarity ratio
Perimeter increase = 6 / 5-1 = 1 / 5
Area increase = (6 / 5) & 178; - 1 = 36 / 25-1 = 13 / 25
So:
The radius of the circle increases by 1 / 5, the circumference of the circle increases by 1 / 5, and the area of the circle increases by 13 / 25