The stationery store brought in 10 boxes of watercolor pens and 10 boxes of erasers. It costs 4 yuan less to buy watercolor pens than to buy erasers. Each box of watercolor pens costs 8.5 yuan. How much is each box of erasers? Equation! Write the equality!

Let each box of rubber X have an equation: 8.5 times 10 plus 4 equals 10x, and then solve the equation

Wang Hua went to a wholesale and retail stationery store to buy pencils and erasers for 30 students in the school art activity group. According to the store rules, if you buy 2 pencils and 1 eraser for each student, you must pay 30 yuan at the retail price; if you buy 3 pencils and 2 erasers for each student, you can pay 40.5 yuan at the wholesale price. It is known that the wholesale price of each pencil is higher than the retail price The price is 0.05 yuan lower, and the wholesale price of each rubber is 0.10 yuan lower than the retail price. How much is the wholesale price of each pencil and rubber in this store?

Suppose the wholesale price of pencils is X Yuan and the wholesale price of rubbers is y yuan, then the retail price of pencils is (x + 0.05) yuan and the retail price of rubbers is (y + 0.10) yuan. According to the meaning of the question, the equation group is 30 [2 (x + 0.05) + (y + 0.10)] = 3030 (3x + 2Y) = 40.5. Solving the equation group is x = 0.25y = 0.3. A: the wholesale price of each pencil is 0.25 yuan and the wholesale price of each rubber is 0.3 yuan

Chinese students went to a stationery store run by wholesalers and retailers to buy pencils and erasers for 30 students in the art activity group of the school
If you buy two pencils and one eraser, you must pay 60 yuan at the retail price. If you buy three pencils and two erasers for each person, you can pay 81 yuan at the wholesale price. It is known that the wholesale price of each pencil is 0.1 yuan lower than the retail price, and the wholesale price of each eraser is 0.2 yuan lower than the retail price. How much is the wholesale price of each pencil and rubber in this store?

Suppose the retail price of each pencil is x yuan, the retail price of each rubber is y yuan, 2x + y = 13 (x-0.05) + 2 (y-0.1) = 40.5/30x = 0.3 yuan, y = 0.4 yuan, so the wholesale price of pencils is 0.3-0.05 = 0.25 yuan, and the wholesale price of rubber is 0.4-0.1 = 0.3 yuan

Zhang Qiang went to the stationery store to buy pencils and erasers for 10 students in the school's art group. He knows that each pencil is m yuan and each eraser is n yuan. If he bought 3 pencils and 4 erasers for each student, he would have to pay () yuan in total

30m+40n

If x ^ 3 + x ^ 2 + X + 1 = 0, find the value of x ^ 2008 + x ^ 2007 + x ^ 2006 + x ^ 2005

=x^2005*(x^3+x^2+x+1)=0

Define the operation | a * B | = | a | B | sin θ, where θ is the angle between vector a and B, if | x | = 2, | y | = 5, xy = 6, then | XY | =?

|x|=2,|y|=5,xy=6,
cosθ=6/10=3/5
sinθ=4/5
Then | XY | = 2 * 5 * 4 / 5 = 8

In the triangle ABC, if the points D, e and F are on the sides of AC, AB and BC respectively, and the quadrilateral cdef is a square, AC = 3 and BC = 2, then the side length of the square is
In the triangle ABC, if points D, e and F are on the sides of AC, AB and BC respectively, and the quadrilateral cdef is a square, AC = 3 and BC = 2, what is the side length of the square?

∵ a quadrilateral cdef is a square
∴DE=CD=CF,DE∥BC
∴ED/BC=AD/AC
Ad = ac-cd = ac-ed, AC = 3, BC = 2
∴ED/2=(2-ED)/3
∴3ED=2(2-ED)
Ed = 4 / 5, that is, the side length of the square cdef is 4 / 5

a> 0, when x ∈ [- 1,1], the minimum value of function f (x) = - x ^ 2-ax + B is - 1, and the maximum value is 1, so that the function can obtain the corresponding x (urgent!
a> When x ∈ [- 1,1], the minimum value of function f (x) = - x ^ 2-ax + B is - 1, and the maximum value is 1. The process of finding the value of X corresponding to the maximum value and minimum value of function is discussed

In a closed interval, the maximum point of a conic (parabola) can only be obtained at the end point and the axis of symmetry. The problem is a parabola with an open term = downward, and since the axis of symmetry (- A / 2) is on the left side of 0, 1 must be the minimum point. If a = B. - A / 2 is (- 1,1], then - A / 2 must be the maximum value. First, let's see if a belongs to (0,2)] and can make the function reach the maximum value 1, Substituting f (x) = a ^ 2 / 4 + B = a ^ 2 / 4 + a = 1, the solution is a = - 2 + 2 * sqrt (2) or - 2-2 * sqrt (2). Sqrt (x) represents x under the root sign. Obviously, the second value is less than zero, and the first value is greater than 0 and less than 2, so the first value meets the condition. At this time, the maximum point is sqrt (2) - 1, and the minimum point is 1
Similarly, if - 1 is the maximum point, then a + B = 2, so a = b = 1

Is the sum of two equal vectors equal to the zero vector
Is the sum of two equal vectors equal to the zero vector? For example, the vector AB plus the vector ba

No
Vector AB and vector Ba are not the same vector, they are the same size and opposite direction vector, the sum must be 0 vector

As shown in the figure, in △ ABC, ∠ a = 36 °, ABC = 40 °, be bisection ∠ ABC, ∠ e = 18 °, CE bisection ∠ ACD? Why?

The reasons are as follows: ∵ a = 36 °, ABC = 40 °, ∵ BCA = 104 °, ∵ ACD = 76 °. ∵ be = ABC, ∵ CBE = 20 °, ∵ e = 18 °, ∵ BCE = 142 °, ∵ ECA = 38 °, ∵ ECD = 38 °,

The stationery store brought in 10 boxes of watercolor pens and 10 boxes of erasers. It costs 4 yuan less to buy watercolor pens than to buy erasers. Each box of watercolor pens costs 8.5 yuan. How much is each box of erasers? Equation! Write the equality!