Huanggang 100 points to break through the mathematics seventh grade |What is the answer to 1 / 2-1 | + | 1 / 3-1 / 2 | + | 1 / 4-1 / 3 | + | 1 / 5-1 / 4 | +... + + 1 / 100-1 / 99 |?

Huanggang 100 points to break through the mathematics seventh grade |What is the answer to 1 / 2-1 | + | 1 / 3-1 / 2 | + | 1 / 4-1 / 3 | + | 1 / 5-1 / 4 | +... + + 1 / 100-1 / 99 |?

Which question? I want to ask you! I want to ask you! I don't know, it's too difficult to write the answer. Where's the difficulty for the teacher? I don't know~~

There is a column of chicken and duck, and chicken is half of duck; eight ducks are flying, six chickens are laying eggs, and then order chicken and duck, duck is three times of chicken, please count, chicken______ One, duck______ Only

Suppose there are x ducks, then there are 12x chickens. From the meaning of the question, we can get 3 (12x-6) = X-8, and the solution is: x = 20, 10 chickens

What is the most difficult step for the seventh grade freshmen to master in solving the application problems of the equations in one variable linear equation?

Your problem is very difficult. The difficulty of solving the problem depends on how much knowledge each person has and the ability to apply the knowledge. There is no most difficult step to master at all. Generally, the types of solving the application problems in the equations listed in Grade 7 are no more than engineering problems, travel problems, tree planting problems, sailing problems, etc

As shown in the figure, ∩ f is the acute angle formed by the bisector of ∩ ABC and the bisector of outer angle ∩ DCE of quadrilateral ABCD, if ∩ a = α, d = β; (1) as shown in Figure 1, α + β > 180 °, use α, β to represent ∩ F
(20 as shown in Figure 2, α + β is less than 180 °, please draw f in the figure and use α and β to represent F

（1）∵∠ABC+∠DCB=360°-（α+β）,
∴∠ABC+（180°-∠DCE）=360°-（α+β）=2∠FBC+（180°-2∠DCF）=180°-2（∠DCF-∠FBC）=180°-2∠F,
∴360°-（α+β）=180°-2∠F,
2∠F=α+β-180°,
■ ∠ f = half (α + β) - 90 °
（2）∵∠ABC+∠DCB=360°-（α+β）,
∴∠ABC+（180°-∠DCE）=360°-（α+β）=2∠GBC+（180°-2∠HCE）=180°+2（∠GBC-∠HCE）=180°+2∠F,
∴360°-（α+β）=180°+2∠F,
F = 90 ° - half (α + β);
(3) When α + β = 180 ° there is no ∠ F

Why do you use the singular to modify a noun? Why do you use the plural

Clothes have the singular and plural
Clothe becomes cloth

As shown in the figure, in equilateral △ ABC, D is a point on BC, ∠ DAE = 60 ° AE intersects the bisector of the outer angle of ∠ ACB at point E

First of all, through AB = AC, ∠ B = ∠ ace, ∠ bad = ∠ CAE (they are equal to 60 ° - DAC, so they are equal), we can know that △ abd and △ ace are congruent, so ad = AE. We also know that ∠ DAE = 60 °, so △ ade is an equilateral triangle

The greatest common divisor of 16 and 24 is (), the least common multiple is (), and the prime factor of decomposing the least common multiple is ()

The greatest common divisor of 16 and 24 is (8), the least common multiple is (48), and the prime factor of decomposing the least common multiple is (48 = 2x3)

Mathematics elective course 2-1.1. Focus on x-axis, a = 6, eccentricity is e = 1 / 3, the standard equation for solving ellipse 2. Focus on x-axis, C = 3, eccentricity is e = 3/

1
The focus is on the x-axis. The major axis is a, a = 6, e = C / a = 1 / 3, C = 2,
b^2=a^2-c^2=36-4=32
The equation is x ^ 2 / 36 + y ^ 2 / 32 = 1
two
The focus is on the x-axis, the long axis A, e = C / a = 3, C = 3, a = 9
b^2=a^2-c^2=81-9=72
The equation is x ^ 2 / 81 + y ^ 2 / 72 = 1

Which of 57, 37, 46, 29, 78, 59, 87, 45, 31, 41 are prime numbers? Which are composite numbers? Prime numbers: composite numbers:

Prime numbers are: 37, 29, 59, 31, 41
The total number is 57,46,78,87,45
Prime: composite = 1:1

As shown in Figure 1, an ideal capacitor with a capacitance of C is connected in series with two resistors with both resistance values of R, and then connected at the electromotive force of & nbsp; At both ends of the DC power supply of E, the internal resistance of the power supply is ignored, and the key K is off. When t = 0, close the key K and connect the circuit. In Figure 2, six kinds of lines a, B, C, D, e and F of voltage V varying with time t are given. Now, three kinds of lines are selected to represent the voltage variation with time t between one of the four points 1, 2, 3 and 4 in the circuit shown in Figure 1. The following four lines are shown The correct choice is ()
A. a、b、fB. a、e、fC. b、d、eD. c、d、e

The internal resistance of the power supply is ignored. After the key K is closed, the voltage between 1 and 4 in the figure is equal to the electromotive force E of the power supply, so the voltage between 1 and 4 can be represented in Figure A. during the capacitor charging process, the current in the circuit gradually decreases, and the image can be represented in the right figure. According to Ohm's law u = IR, the voltage between 1, 2, 3 and 4 gradually decreases