Application of quadratic equation of one variable In January 2010, the sales volume of Renming shopping mall was 1 million yuan, and the sales volume decreased by 10% in February. In March, the shopping mall took measures to reform the traffic strategy, so that the monthly sales volume increased significantly, and the sales volume in April reached 1.296 million yuan

Application of quadratic equation of one variable In January 2010, the sales volume of Renming shopping mall was 1 million yuan, and the sales volume decreased by 10% in February. In March, the shopping mall took measures to reform the traffic strategy, so that the monthly sales volume increased significantly, and the sales volume in April reached 1.296 million yuan

According to the meaning of the title: February sales: 100 * (1-10%) = 900000 yuan,
Suppose the average growth rate of sales in March and April is x, then:
90*（1+x)^2=129.6
(1+x)^2=1.44
1 + x = 1.2 1 + x = - 1.2 (rounding off)
x=0.2=20%
That is to say, the average growth rate of sales in March and April is 20%

The process of solving two practical problems of quadratic equation with one variable is described;
According to statistics, 1260 e-cards were sent to each other at Christmas last year. How many students were there in class 1?
2. Everyone should shake hands with each other at a class gathering on the school day. It is known that 300 times of shaking hands have been made by the students present at the meeting. How many students are there?

1. Suppose there are X students in class 1 of grade 3. (x + 6) (x + 5) = 1260 x ^ 2 + 11x-1230 = 0 (x + 41) (X-30) = 0, x + 41 = 0, X-30 = 0, x = - 41 (not suitable for the topic) x = 30 A: there are 30 students in class 1 of grade 3. 2. Suppose there are X students in this meeting. X (x-1) / 2 = 300X ^ 2

On the exercise and solving process of the application problems of quadratic equation of one variable
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In January 2010, the sales volume of Renming shopping mall was 1 million yuan, and the sales volume decreased by 10% in February. In March, the shopping mall took measures to reform the traffic strategy, so that the monthly sales volume increased significantly, and the sales volume in April reached 1.296 million yuan
According to the meaning of the title: February sales: 100 * (1-10%) = 900000 yuan,
Suppose the average growth rate of sales in March and April is x, then:
90*（1+x)^2=129.6
(1+x)^2=1.44
1 + x = 1.2 1 + x = - 1.2 (rounding off)
x=0.2=20%
That is to say, the average growth rate of sales in March and April is 20%

If a, B, C and D are not equal to each other, then a + B + C + D =?

A = - 1. Or B = 1 or C = 3 or C = - 3
So a + B + C + D = 0

What is the rated power of 400W power supply
I bought a power supply! The seller said it was 400W. The rated power on the power supply is 300W, and the maximum power is 400W. Is this power supply 400W

It should be 300W, but its maximum load is 400W

A very simple mathematical problem. To process, thank you
A and B are employed by the farm to sow flowers. Each person is responsible for half of the 10 mu of land. A is responsible for the East, and B is responsible for the West. It takes 20 minutes for a to cultivate one mu of land, and it takes 40 minutes for B. when sowing, the speed of B is 3 times that of A
The total wage of two people is $100. If the wage is divided according to the amount of farming, how much can B get?

B got 62.5 US dollars. The cultivated land and sowing were divided into 50 US dollars. B ploughed 1 / 4 divided by (1 / 20 + 1 / 40) + 4 / 1 = 1 / 3 1 / 3 * 50 = 16 2 / 3 US dollars. B sowed 1-10 / 3 = 20 / 3 20 / 3 * 1 / 2 = 10 / 3 10 / 3 divided by (1 + 1 / 3) = 5 / 6 5 / 6 * 2 / 1 = 5 / 12 2 / 1 + 5 / 12 = 11 / 1211 / 12 * 50 = 45 5 / 6

Should the air switch be connected before or after the electric energy meter

The household air switch is only used to protect the short circuit fault of the load connected by the user, so the air switch is generally connected after the meter. When the meter has a short circuit fault, the power supply is disconnected through the upper air switch

(half x-3) (half x + 3) is calculated by multiplication formula

Quarter (x ^ 2) - 9
Let 0.5x = a, 3 = B
Formula: (a-b) (a + b) = (a) ^ 2 - (b) ^ 2
So the answer is (0.5x) ^ 2 - (3) ^ 2 = 0.25 (x ^ 2) - 9

In VML water, mgnaoh was added. After all the solids were dissolved, the density of the solution was measured to be pg / cm3
Beginners, which is a kind brother and sister, help me

Amount of solute NaOH: M / 40
Volume of sodium hydroxide solution: (V * 1 + m) / P ml = 0.001 (V * 1 + m) / P L
The unit of volume should be converted into liters
The amount and concentration of NaOH solution are as follows:
1000(m/40) /[(v*1+m)/P]=25mP/(V+m) mol/L

Please help me finish this new definition problem
∵P#Q=5P+3Q
∴(X#9)#2=191
Left = (x × 9) × 2
=(5X+27)#2
=A#2
=5A+6
=5×（5X+27)+6

Left = 5 × (5x + 27) + 6
=25x+135+6
=25x+141
Right = 191
25x+141=191
25x=50
x=2