A series of linear equations with one variable An individual taxi driver is required to pay 1400 yuan per month and 0.5 yuan per kilometer for gasoline; another state-owned taxi company is required to pay 1.2 yuan per kilometer for gasoline without salary (1) If the unit runs an average of a kilometer per month, how much will each of the two car rental schemes cost? (2) Please design a plan for the unit, so that the unit can choose a reasonable way to rent a car

(1) Scheme 1: 1400 + 0.5A scheme 2: 1.2A (2) 1400 + 0.5A = 1.2A a = 2000 three cases: 1. When the running distance is less than 2000, scheme 2 2. When the running distance is more than 2000, scheme 1 3. When the running distance is equal to 2000, scheme 2, scheme 1

1. When a and B run on the 400 meter circular track, if they run in the same direction, they meet every 3 minutes. If they run in the opposite direction, they meet every 40 seconds. What's the speed of a and B? (a is faster than B)
2. In the countryside, it is often necessary to straighten the curved river course to reduce the silt. Please tell us the mathematical reason. In the scenic spots, the bridges on the lake are often zigzag rather than straight. Give us the reasons for building bridges like this
3. From 15:00 to 24:00, the minute hand of the clock turns an angle of () degrees, and the hour hand turns an angle of () degrees

Shouldn't we use quadratic equation in grade one?
1: Let the velocity of a be x and the velocity of B be y
180（x-y）=400
40（x+y）=400
The solution is x = 55 / 9
y=35/9
2: The shortest line between two points
The arch is stable and the force is uniform
3: Minute hand 54 ° hour hand 0.9 degree

For a kind of concrete, 3 parts of sand, 2 parts of stone and 1 part of cement are mixed together, and the sand accounts for 30% of the concrete_ The stone is less than sand (& nbsp; & nbsp; & nbsp;) (& nbsp; & nbsp;). If 2 tons of cement is needed, it can be mixed_ Tons of concrete

3 + 2 + 1 = 6 (parts) 3 △ 6 = 12 (3-2) △ 3 = 13; 2 △ 1 × 6 = 12 (tons) a: sand accounts for 12% of concrete, and stones are 13 less than sand. If 2 tons of cement are needed, 12 tons of concrete can be mixed. So the answer is: 12, 13, 12

Kneel down to find a mathematical problem, let u = R, a = {x | x2 + ax-12 = 0}, B = {x | BX + b2-28 = 0}, if a intersects B and the complement {2} of u is ab
Kneel down to find a mathematical problem, let u = R, a = {x | x2 + ax-12 = 0}, B = {x | BX + b2-28 = 0}, if the complement of a intersection B to u is {2}, find the value of a and B

X = 2 is the root of x2 + ax-12 = 0
2^2+2a-12=0
a=4
x^2+4x-12=0
(x-2)(x+6)=0
So: A has another element - 6
X = - 6 is the root of BX + b2-28 = 0
-6b+b^2-28=0
B = 3 + (root 37), or B = 3 - (root 37)

There are 72 more books than comic books, and books are three times as many as comic books. How many storybooks do you have

We can't find out the number of story books. We can only find out that there are 72 / (3-1) = 36 comic books and 36 * 3 = 108 books. If books only include comic books and story books, there are 108-36 = 72 story books

On the number axis, the point with absolute value less than 3 and two unit length away from - 2 represents the number

The absolute value is less than 3: that is, the number is greater than - 3 and less than + 3,
Two points of unit length from - 2: namely - 4 or 0;
So the number is zero

If the quadratic function f (x) = x & # 178; + BX + C is monotone in the interval [- 1,1], then the value range of real number B is

Solution function f (x) = x & # 178; + BX + C
The axis of symmetry is x = - B / 2
In addition, f (x) = x & # 178; + BX + C is a monotone function in the interval [- 1,1]
That is - B / 2 ≤ - 1 or - B / 2 ≥ 1
That is, B ≥ 2 or B ≤ - 2

We walked into the nature museum with a happy mood and relaxed pace

We walked into the nature museum with happy mood and relaxed steps

Given that O is the origin of coordinates, point m (A-2, b), and (A-2) &# 178; + (B-3) &# 178; = 0, if point n is on the x-axis and the area of △ mon is 6, the coordinates of point n can be obtained

Because (A-2) & sup2; + (B-3) & sup2; = 0, so a = 2, B = 3, so m (0,3) is on the y-axis, because n can be set on the x-axis, the coordinate of n is (x, 0). According to the meaning of the title, we get 〡〡× & frac12; × 3 = 6, that is 〡〡〡 = 4, so x = ± 4
So the coordinates of N are (4,0) or (- 4,0)

It is known that y = f (x) is a monotone increasing function in its domain of definition, and its inverse function is y = F-1 (x)
If the absolute value of the inverse function of F (x + 1) is less than or equal to 3, then the value range of X is?

The image of y = f (x + 1) passes a (- 4,0); B (2,5) passes (- 3,0) according to left plus right minus y = f (x); (3,5)
The inverse function of F (x + 1) is over (0, - 3);, (5,3)
　　　｜x｜|

For a kind of concrete, 3 parts of sand, 2 parts of stone and 1 part of cement are mixed together, and the sand accounts for 30% of the concrete___ The stone is less than sand (& nbsp; & nbsp; & nbsp;) (& nbsp; & nbsp;). If 2 tons of cement is needed, it can be mixed___ Tons of concrete