In △ ABC, D and E are the midpoint of BC and ad respectively, and s △ ABC = 4cm2, then s △ Abe=______ ．

∵ D is the midpoint of BC, ∵ s △ abd = 12S △ ABC = 12 × 4 = 2cm2, ∵ e is the midpoint of AD, ∵ s △ Abe = 12S △ abd = 12 × 2 = 1cm2

1、 There is a pasture where grass grows at a constant speed every day (i.e. the amount of grass increases every day is equal). If 24 cows are released, grass will be eaten in 6 days. If 21 cows are released, grass will be eaten in 8 days. Suppose that the amount of grass eaten by each cow is equal
(1) If you put 16 cows, how many days can you eat the grass?
(2) How many heads can you put at most if you want to make the grass never finish?
2、 Party A and Party B walk towards each other at the same time in AB and meet at point E in AB's journey. After Party A continues to walk towards place B, Party B takes a 14 minute rest and then walks towards place A. after arriving at B and a, Party A and Party B turn back immediately and still meet at place E. given that Party A walks 60 meters per minute and Party B walks 80 meters per minute, how many meters is the distance between a and B?
A——————————E——————————————B
Party A and Party B
Tell me the way to solve the two problems. It's too difficult for me to teach others

Suppose that the amount of grass per cow per day is x, the amount of grass per day is y, the amount of grass per cow per day is a
It can be seen from the question: a + 6y = 24 * 6x (1)
a+8y = 21*8x（2）
a+yz = 16xz （3）
(2) - (1), y = 12x (4), that is: the daily grass consumption of 12 cattle is just equal to the daily growth, so if we want to make the grass never finish, we can grazing 12 cattle at most
(3) (2), we get: (Z-8) y = 8x (2z-21) (5)
From (4) and (5), z = 18
A: if you graze 16 cows, you can eat the grass in 18 days
In order to make the grass never finish, grazing 12 cattle at most
2. The speed ratio of a and B is 60:80 = 3:4
For the first time, a takes 3 / 7 of the whole journey, and B takes 4 / 7 of the whole journey
The second meeting, a and B a total of two people walk the whole journey
B: 4 / 7 * 2 = 8 / 7
A goes the whole way: 3 / 7 * 2 = 6 / 7
Let the whole process be X
（8/7x/60-14）*80=6/7x
x=1680

There is a circular fountain with a diameter of 20m in the community. My grandfather walks around the fountain five times every morning. How many meters does my grandfather walk every morning?
The specific formula,

3.14 × 20 × 5 = 314 (m)

Calculate 24 points with five, five, five and one

(5-1/5)*5=24

Which point on the logarithmic curve y = ln X has the smallest radius of curvature

How to get the radius of rate is determined by the formula, which is found in the first volume of advanced mathematics. It is not easy to type here. After calculating according to the formula, we can solve this problem by calculating the most valuable knowledge point by derivation

In the following statement about the density formula P = m / V, what is correct?
A. The density is proportional to the mass of the object
B. Density is inversely proportional to the mass of an object
C. Density is related to the mass and volume of an object
D. The density of an object can be calculated according to its mass and volume

It is proved that if the side length of the bottom of a prism is a and the area of side a is twice the area of the bottom, then its volume is

Its volume is 2a and 179;

If xy = m and x ^ 2 / 1 + y ^ 2 / 1 = n, then (X-Y) ^ 2=

1/x²+1/y²=n
(x²+y²)/(xy)²=n
x²+y²=m²n
(x-y)²
=x²+y²-2xy
=m²n-2m

Build a cement road with a width of 3.6 meters and a thickness of 20 cm. If 7.2 cubic meters of concrete is mixed, how many meters can it be paved?

20 cm = 0.2 m, 7.2 △ 3.6 × 0.2, = 7.2 △ 0.72, = 10 m; a: it can be paved for 10 m

Let a > b > C > 0, then the minimum value of 2A2 + 1ab + 1a (a − b) - 10ac + 25c2 is______ ．

∵ a > b > C > 0, ∵ 2A2 + 1ab + 1a (a − b) - 10ac + 25c2 = A2 + 1B (a − b) + (a − 5C) 2 ≥ A2 + 1 (B + a − B2) 2 + (a − 5C) 2 = A2 + 4a2 + (a-5c) 2 ≥ 2A2 · 4a2 + 0 = 4

In △ ABC, D and E are the midpoint of BC and ad respectively, and s △ ABC = 4cm2, then s △ Abe=______ ．