Elementary three quadratic equation of one variable, online, etc As shown in the figure, an isosceles trapezoid flowerbed should be designed. The upper bottom of the flowerbed is 100 meters long, the lower bottom is 180 meters long, and the distance between the upper and lower bottom is 80 meters. There is a transverse corridor at the middle line of the two waist, and there are two longitudinal corridors between the upper and lower bottom. The width of each corridor is equal. The area of the corridor is one sixth of the area of the ladder. How many meters should the width of the corridor be?

If the width of the corridor is x m, then:
S trapezoid = (100 + 180) * 80 / 2 = 11200 (m ^ 2),
Trapezoid median line length = (100 + 180) / 2 = 140 (m),
Area of corridor = 140x + 2 * 80x-2x ^ 2 = 11200 / 6
The solution is: x = 6.5 (m)

The charging standard of an advertising company for advertising production is: in the area as a unit, within the specified area of a (M2), each advertising fee is 1000 yuan. If it exceeds a (M2), in addition to the basic advertising fee of 1000 yuan, the excess part should be paid by 50A yuan per square meter. The following table is the company's record of the advertising area and charging situation of two users: single Tobacco company 61400 food company 31000 red star company to make a large public service advertisement, the material shape is rectangular, its four sides are blank, as shown in the figure, if the upper, lower each empty 0.25m, left and right each empty 0.5m, then the area of the blank part is 6m2 The rectangular part in the middle is the advertising area. If the advertising cost of this advertisement is 2600 yuan, what is the area of the blank part around?

Let the width of rectangular material be XM and the length be (x + 1) M. from the meaning of the title, we can get 2 × 0.25 (x + 1) + 2 × 0.5 (x-0.25 × 2) = 6 and the solution is x = 4

It is known that X1 and X2 are the two real roots of the equation (X-2) (x-m) = (P-2) (P-M) about X. (1) find the value of X1 and X2; (2) if X1 and X2 are the lengths of the two right sides of a right triangle, when the real numbers m and P satisfy what conditions, the area of the right triangle is the largest? And the maximum value is obtained

(1) The original equation is changed as follows: X2 - (M + 2) x + 2m = P2 - (M + 2) P + 2m, ｜ x2-p2 - (M + 2) x + (M + 2) P = 0, (X-P) (x + P) - (M + 2) (X-P) = 0, that is, (X-P) (x + p-m-2) = 0, ｜ X1 = P, X2 = m + 2-P; (2) according to (1), the area of right triangle is 12x1x2 = 12p (...)

The extension of Newton's second law
How to use Newton's second law of the system is the equation relationship between the external force and the internal force,
Is it possible that the forces in the system are not in a straight line?

Newton's second law is simplified as follows: F = ma, for an object, the resultant force is f (he), and the total acceleration a (he) satisfies: F (he) = m * a (he). If f (he) is the internal force components F1, F2, F3, F4, F5, the result is that f (he) is the vector sum of each component force, there is f (he) = (F1 + F2 + F3

It is known that the circumference of an isosceles triangle is 20. The functional expression of expressing the base length y as the waist length x is y = 20-2x, and the value range of its independent variable is
A.0＜x＜10
B.5＜x＜10
C. All real numbers
D.x＞0

Answer B
According to "the sum of the two sides of the triangle is greater than the third side", we get 2x > y, that is, 2x > 20-2x
Analysis: to find the value range of independent variable in geometry problem, we should consider not only x > 0, but also "the sum of two sides of triangle is greater than the third side"

As shown in the figure, the hook code with mass m moves vertically upward under the action of the spring scale. If the indication of the spring scale is t and the acceleration of gravity is g, then ()
A. When t = mg, the mechanical energy of hook code does not change. When B. T < mg, the mechanical energy of hook code decreases. When C. T < mg, the mechanical energy of hook code increases. When D. T > mg, the mechanical energy of hook code increases

No matter whether the tension of the spring scale is greater than gravity, less than gravity or equal to gravity, in the process of vertical upward movement, the tension does positive work. According to the functional relationship, the mechanical energy of the hook code increases. So C and D are correct. A and B are wrong. So CD is selected

There are 99 plums, two people take turns, each time the rules take 1-5, can not take, who got the last one who lost, if you take first, what strategy do you have to win?

(99-1) divided by (1 + 5) = 16 and remaining 2
Me: first take 2, then the other party takes a few, I take 6-A few
One opponent, five for me, and the last one for him
Thank you!

Neutron star is the last form of stellar evolution, which: (1) there is a star with uniform density, rotating around its own geometric axis of symmetry with angular velocity W

Neutron star is not the final state of a star, it needs further evolution. Because of its high temperature and fast energy consumption, its life span is only several hundred million years. When its energy consumption is finished, the neutron star will become a black dwarf that does not emit light

In the arithmetic sequence an, Sn is the sum of the first n terms, A4 + A7 = 10, then S10 is

Because an is an arithmetic sequence
So a1 + A10 = A4 + A7 = 10
S10 = (a1 + a10)×10÷2
= 10×10÷2
= 50

A car running along a straight road, the speed is 36km / h, the acceleration obtained after braking is 4m / S ^ 2, and the displacement of the car in the last two seconds is calculated
Please solve it as soon as possible
What exactly is it

S = 1 / 2att = 1 / 2 * 4 * 2 * 2 = 8M

The extension of Newton's second law How to use Newton's second law of the system is the equation relationship between the external force and the internal force, Is it possible that the forces in the system are not in a straight line?

It is known that the circumference of an isosceles triangle is 20. The functional expression of expressing the base length y as the waist length x is y = 20-2x, and the value range of its independent variable is A.0＜x＜10 B.5＜x＜10 C. All real numbers D.x＞0