1. A car drives from a to B. the first 3 / 1 section is an ordinary highway, and the other sections are expressways. It is known that the speed of the car on the ordinary highway is 60km / h, and the speed on the expressway is 100km / h. The car has driven from a to B for a total of 2.2h, This paper presents a problem solved by a system of linear equations of two variables, 2. From a to B, you need to go downhill first; if you go through the level road at the speed of 15 km / h, you can get to B for 1 hour and 6 minutes; if you come back, you need to go through the level road at the speed of 12 km / h, and then go up the slope at the speed of 8 km / h. If you go back to a for 1 hour and 30 minutes, how many kilometers are there between a and B? 3. Party A and Party B both run on the circular road at the same speed. If they start from the same place and walk in opposite directions at the same time, they meet every two minutes; if they walk in the same direction, they meet every six minutes. It is known that Party A runs faster than Party B, how many laps do Party A and Party B run in each minute?

one
Problem: find the distance between AB and two places
Let the distance of ordinary highway be x and that of Expressway be y
（1） 2X=Y
(2) X/60+Y/100=2.2
The solution is x = 60km, y = 120km
Then the distance between AB and ab is x + y = 180km
three
Set up: A and B run X and Y laps each minute,
6 (X-Y) = 1
2 (x + y) = 1
x=1/3,y=1/6,
A: they run 1 / 3 and 1 / 6 laps each minute

Find out three mathematical calculation problems in grade one of junior high school
The first on rational numbers
The second one is about algebraic expressions
The third one is about the equation of degree one variable
They are the contents of the second, third and fourth chapters of the first semester of Junior High School of Jiangsu Education Press
Not too hard, not too easy
I need it tomorrow. It's urgent! It's a calculation problem!
Answer and problem-solving process also said

These topics are very good, very detailed

There are 126 trees planted in the fifth grade, 32 more than twice that in the fourth grade, and 32 more than that in the third grade?

(126-32) / 2 = 47 fourth grade
47 * 2 + 32 = 126 (trees) Third grade
126 -- 47 = 79 (trees)
A: there are more than 79 trees planted in the third grade

1. Eight fifths of a number is more than two fifths of it. 18. What's the number?
2. One third of a number is six. How much is it to increase it by one half?

1. The number is: 18 (8 / 5-2 / 5) = 15
2. The number is: 6 / 1 / 3 = 18
Increasing it by half is: 18x (1 + 1 / 2) = 27

The average number of a, B and C is 56, the sum of a and B is 147, and the sum of B and C is 123. What are the numbers of a, B and C?

A 45. B 102. C 21

If the operation ⊙ a ⊙ B = AB + 2A + B is defined on R, then the value range of real number x satisfying x ⊙ (X-2) < 0 is ()
﹙A﹚﹙0,2﹚ ﹙B﹚﹙﹣2,1﹚ ﹙C﹚﹙﹣∞,﹣2﹚∪﹙1,﹢∞﹚ ﹙D﹚﹙﹣1,2﹚

The sum of a and B numbers is 305.8. The decimal point of B number will be equal to a number after moving one place to the right. What are the numbers of a and B?

X+X/10=305.8
A = 278
B = 27.8

The maximum value of function y = - X & sup2; - 2aX (0 ≤ x ≤ 1) is a & sup2;, the value range of real number a

y=-X²-2AX
=-(x+A)²+A²
When x = - A, take the maximum value a & # 178;
Then - a ∈ [0,1]
That is, the value range of real number a [- 1,0]

There are two cups. Cup a contains 50ml of water and cup B contains 120ml of water. If you look at the same white sugar in two cups, 35g in cup a and 80g in cup B, which cup is sweeter after mixing? Who can help me solve this problem

The general concentration question 35 / 50 80 / 120 is sweeter, so the cup a is sweeter. But in fact, the answer may be the same, because 35 / / 50 = 0.7 80 / 120 = 0.66667 is about 0.7
Of course, this is based on the primary school, otherwise we have to consider the solubility and saturation

Let the matrix A = 0.1 A, we know that the fundamental solution system of homogeneous linear equations AX = 0 contains two vectors, 1 a 0.1
Finding the value of a and finding the general solution of the structural formula AX = 0

Solution: known by 4-R (a) = 2, so r (a) = 2
A -->
r3-r1
1 2 1 2
0 1 a a
0 a-2 -1 -1
r1+r3, r2+ar3
1 a 0 1
0 (a-1)^2 0 0
0 a-2 -1 -1
Because R (a) = 2, a = 1
At this time, a - >... - >
1 1 0 1
0 0 0 0
0 -1 -1 -1
r3*(-1), r3r2
1 1 0 1
0 1 1 1
0 0 0 0
The general solution of the equations is: C1 (1, - 1,1,0) ^ t + C2 (1,0,1, - 1) ^ t

There are 126 trees planted in the fifth grade, 32 more than twice that in the fourth grade, and 32 more than that in the third grade?

1. Eight fifths of a number is more than two fifths of it. 18. What's the number? 2. One third of a number is six. How much is it to increase it by one half?