1. The foundation of a teaching building in Zhaohui primary school is a rectangle with a length of 3.80 meters and a width of 30 meters. According to the plan, its width is 15 cm, and how long should it be? 2. The water supply company needs to install a 31 meter long water pipe. There are two kinds of water pipes of 3 meters and 5 meters. It is known that each pipe of 3 meters is 32 yuan. How much will it cost to install this pipe? 3. Xiaoming asked Xiaohong, "how many rabbits and chickens do you raise in your family?" Xiaohong answered very interestingly. He said, "I raise more rabbits than chickens. Chickens and rabbits have 24 feet in total. Guess how many rabbits and chickens do you raise in my family?" The multiplication and division signs are written in Chinese characters

The scale of 1.30 M = 3000 cm is 15:3000 = 1:200, 80 m = 8000 cm, 8000 times 1 / 200 = 40 (CM). 2. Less conditions, you can also divide 31 by 3 = 10 (root) 1 (m) (10 + 1) times 32 = 352 (yuan), or let a 5 m x yuan, 32 = 5 times 4 + 3 times 4, get 4x + 1283

It is stipulated that the symbol "△" is to select the larger number in the two numbers, and "@" is to select the smaller number in the two numbers. Then, what is the value of [(7  3) △ 5] × [5  3  7]?

The value of [(7-3) △ 5] × [5-3 △ 7], = [3-5] × [5-7], = 5 × 5, = 25, a: the value of [(7-3) △ 5] × [5-3 △ 7] is 25

Coordinate formula
A pool has an inlet pipe and an outlet pipe. Open the inlet pipe for 8 minutes to fill the pool, and open the outlet pipe for 12 minutes to drain all the water in the pool. If you open the inlet pipe for 1 minute, and then open the outlet pipe at the same time, how long will it take to fill the pool? There are other rewards

Let v be the volume of the pool, and V be the velocity of water inflow V / 8, V / 12 V / 8 + (V / 8-v / 12) * t = v. the solution is t = 21, and the first minute is 22 minutes

The following equation is reduced to a general form and its quadratic coefficient, primary coefficient and constant term are written out: (1) x & # 178; = x + 1
（2）4x（x+1)-x(x-2)=2
Solve the following equations: (1) (3x + 2) &# 178; - 7 = 0; (2) 2x & # 178; - 3x-3 = 0; (3) 4x & # 178; - X-1 = 0

(1) X & # 178; = x + 1, X & # 178; - X-1 = 0, coefficient of quadratic term 1, coefficient of primary term - 1, constant term - 1 (2) 4x (x + 1) - x (X-2) = 2 3x & # 178; + 6x-2 = 0, coefficient of quadratic term 3, coefficient of primary term - 6, constant term - 2 solve the following equation: (1) (3x + 2) &# 178; - 7 = 0 (3x + 2) &# 178; = 7 3x + 2 = ± √

Write out the general form of the following equation, and point out the coefficient of the first-order term, the first-order function and the constant term ① X & # 178; - 3 = 2x ② 3x (x-1) = 2 (x + 1) + 8

（1）
x²-2x-3=0
The coefficient of quadratic term is 1, the coefficient of primary term is - 2, and the constant term is - 3
（2）
3x²-5x-10=0
The coefficient of quadratic term is 3, the coefficient of primary term is - 5, and the constant term is - 10

The coefficient of quadratic term of equation 3x (x + 1) = 0 is, the coefficient of primary term is, and the constant term is

3x (x + 1) = 0. If you multiply 3x, you will get
3x + 3 = 0
So the quadratic term is 3x
Once there is no item
The constant term is 3

Change the equation (2x + 1) (3x-2) = the square of X + 2 into a general form and write out the coefficients of quadratic term, coefficient of primary term and constant term

（2X+1）(3X-2)=X²+2
6X²-4X+3X-2=X²+2
5X²-X-4=0
The quadratic coefficient is 5,
The coefficient of the first term is - 1
The constant term is - 4

The output of a certain steel plant in January last year was 5000 tons, which rose to 7200 tons in March. If the average monthly growth rate of the two months is the same, the output in February will be 5000 tons______ Tons

Suppose that the percentage of average monthly growth is x.5000 × (1 + x) 2 = 7200, (1 + x) 2 = 1.44, the solution is X1 = 20%, X2 = - 2.2, (not suitable for the problem, omit) ‖ the output in February = 5000 × (1 + 20%) = 6000 tons

Market research shows that when the selling price is 2900 yuan, an average of 8 refrigerators can be sold every day; when the selling price is reduced by 50 yuan, an average of 4 more refrigerators can be sold every day; how many yuan should the selling price be reduced to make the average profit of this refrigerator reach 5000 yuan every day?

Suppose that the price of each refrigerator should be x yuan. According to the meaning of the question, we get (x-2500) (8 + 2900 − X50 × 4) = 5000. Solving the equation, we get X1 = x2 = 2750. After testing, X1 = x2 = 2750 meets the meaning of the question. Answer: the price of each refrigerator should be 2750 yuan

Mathematical quadratic equation with one variable
X ^ 2 = Z ^ 2-7.5z + 16, use X to express Z

Z ^ 2-7.5z + (16-x ^ 2) = 0, take Z as an unknown number and X as a known number, and then solve the equation. By using the formula of the root of quadratic equation with one variable, z = 2 {7.5 plus minus root sign [7.5 ^ 2-4 (16-x ^ 2)]}