If the car runs 40km / h in the first half of the planned time and 50km / h in the second half of the planned time, it will arrive on time. However, when the car runs 40km / h to 40km away from the midpoint of AB, it breaks down. After stopping for half an hour, it advances 55km / h, and it still arrives at B on time. The distance between a and B and the original plan are calculated Travel time

Suppose the distance between a and B is XKM, and the original planned driving time is YH. From the meaning of the question, 40 × Y2 + 50 × y2 = XX2 − 4040 + x2 + 4055 = y − 12, the solution is: x = 360y = 8. Answer: the distance between a and B is 360km, and the original planned driving time is 8h

11(1+x）²=18.59

(1+x）²=18.59 /11
(1+x）²=1.69
1+x=±1.3
x1=-1+1.3=0.3
x2=-1-1.3=-2.3

2,7,17,32,52,57,67,75,90100. According to the given data, a general formula for calculation is derived
Is to draw a conclusion that the equation formula can meet the given number! At the same time, it can also calculate the subsequent number

A【n】-A【n-1】=5×（n-1）
Make a list of each item, add it up and eliminate it

If (2x ^ 2-x-1) ^ 3 = A0 + a1x + a2x ^ 2 + a3x ^ 3 + a4x ^ 4 + a5x ^ 5 + a6x ^ 6, then a1 + a3 + A5=

Calculate A1, A3 and A5 respectively and then add them together

How much is 6 minus 2 / 7 minus 5 / 7

2 out of 6-7 to 5 out of 7
=6 - (2 / 7 + 5 / 7)
=6-1
=5 [this problem should use the nature of subtraction for simple operation

What grade do I learn to divide polynomials by polynomials? I don't want it in primary school. It's similar to factorization

First semester of junior high school

Fill the 6 numbers 4 / 6 / 9 / 10 / 11 / 12 in 3 () 1 () 5 () 7 () 2 () 8 () brackets so that the sum of every four numbers equals 26

There is no solution
∵3+1＝4,
The sum of the first two brackets = 26-4 = 22,
You can only fill in 10, 12,
And 2 + 8 = 10
The sum of the last two brackets = 26-10 = 16,
You can only fill in 4, 12 or 6, 10,
12 or 10 has been used in the first two brackets, so there is no solution

A truck full of goods is 2.5m in height and 1.6m in width. The upper part of a factory door is semicircle (2m in diameter) and the lower part is rectangle (2.3m in height and 2m in width)
Can you live,

Analysis: assuming that the height limit of a truck with a width of 1.6m passing through the factory gate (maximum height of the truck) is h, it is easy to know that the truck should take the center of the semicircle on the upper part of the factory gate as the symmetry center, and it is most reasonable for both sides to pass symmetrically. Therefore, the truck is bounded by the center of the semicircle, and the width of each side is 0.8m, and the lower part of the factory gate is rectangular (2.3m high, 2m wide)

A two digit number, minus three times the sum of its digits, results in 23. The quotient of this two digit number divided by the sum of its digits is 5, and the remainder is 1. What are these two digits?

Let X be the ten digit number of this two digit number, and y be the number of each digit. According to the meaning of the question, we get 10x + y − 3 (x + y) = 2310 x + y = 5 (x + y) + 1, and the solution is x = 5Y = 6, so this two digit number is 56. A: this two digit number is 56

Woodworking a 50 cm long, 40 cm wide, 16 cm high drawer at least to use wood how many square centimeters?

50x40 + 50x16x2 + 40x16x2 = 4720 square centimeter