The food chain is formed by living things for the sake of other living things

Food chains are formed by organisms feeding on other organisms in order to survive
I don't know if it's right

Based on the data from the textbook, the group discussed how the number of organisms along the food chain and the energy stored in the organism change?
RT

First of all, the energy is decreasing step by step. The energy of the first trophic level is the highest, and the energy transfer is about 10-20%. The former is the lowest value of energy transfer, while the latter is the highest. Therefore, the number of organisms before the trophic level will be more, in order to supply the survival of high trophic level organisms

Ecosystem food chain and food web

Grass → rabbit → Fox
Grass → mouse → owl and snake
Grass → herbivorous insects → insect eating birds → owls
Grass → herbivorous insect → spider → snake → Owl
Grass → herbivorous insects → spiders → insect eating birds → owls
Grass → herbivorous insect → spider → frog
Grass → herbivorous insect → frog

It is known that the sequence {an} is an arithmetic sequence, and the sum of the first n terms is Sn, A3 = 7, S4 = 24. The general term formula of the sequence {an} is obtained

a3 = a1 + 2d = 7
S4 = 4a1 + 6d = 24
The solution is as follows
a1 = 3
d = 2
So an = 2n + 1

If a particle moves in a straight line with an initial velocity of 2m / s and the velocity becomes 14m / s after a period of time, the velocity of the particle in the middle of the period is
_ The velocity in the middle of M / S is_ m/s

Midpoint time v = 8
Middle distance v = 10
There are two formulas V in which time = V initial + V final / 2
The square of the path in v = the square of the beginning of V + the square of the end of V / 2
Just bring the formula
You can try

Mom and dad work in the same company. Dad works for 5 days and has a day off. Mom works for 4 days and has a day off. How many days can they have a day off at the same time?

The least common multiple of 5 and 4

（X-0.7/0.2） - （X-1/0.1）=1
0.2 x-0.7 minus 0.1 X-1 equals 1
The best solution! The best solution!

（X-0.7）/0.2 - （X-1）/0.1=1
According to your Chinese description, this formula should be like this
（X-0.7）*5 - （X-1）*10=1
5x-3.5-10x+10=1
5x=5.5
x=1.1

On the equation MX & # 178; + (M + 3) x + 2m + 14 = 0 of X, which has two real roots, one is greater than 4 and the other is less than 4, the value range of M is obtained
(2) Finding the value range of real number m in [0,4]

(1) MX & # 178; + 2 (M + 3) x + 2m + 14 = 0 has two different real roots (m ≠ 0), one is greater than 4, the other is less than 4
It is equivalent to the intersection of parabola f (x) = MX & # 178; + 2 (M + 3) x + 2m + 14 and x-axis, one on the left side of 4 and the other on the right side of 4
The drawing shows that:
When m > 0, the opening is upward and there is f (4)

Use equations to solve. There must be a normal process
Two C-shaped steel plates and one D-shaped steel plate can be made from one fast A-shaped steel plate; one C-shaped steel plate and two D-shaped steel plates can be made from one B-shaped steel plate. Now 15 C-shaped steel plates and 18 steel plates are needed. How many A-shaped steel plates and B-shaped steel plates can be used exactly?

There are x A-type steel plates and Y B-type steel plates
2X+Y=15①
X+2Y=18②
①×2-②
3X=12
X=4
Substituting x = 4 into (1) y = 7
So there are 4 A-type steel plates and 7 B-type steel plates

Let A1 = 256 in the equal ratio sequence {an}, the sum of the first n terms be Sn, and Sn, Sn + 2, Sn + 1 form the equal difference sequence,
1) Finding the value of Q
2) Let TN = a1a2a3 Compare the size of T8, T9 and T7

Sn=a1(1-q^n)/(1-q)
Sn+1=a1[1-q^(n+1)]/(1-q)
Sn+2=a1[1-q^(n+2)]/(1-q)
2Sn+2=Sn+Sn+1
a1[1-q^(n+1)]/(1-q)+a1[1-q^(n+1)]/(1-q)=2a1[1-q^(n+2)]/(1-q)
2q^2-q-1=0
(2q+1)(q-1)=0
Q = - 1 / 2 or q = 1
T8=a1a2a3…… a8=a1^8q^23
T9=a1a2a3…… a9=a1^9q^31
T7=a1a2a3…… a7=a1^q^16
When q = 1, T9 > T8 > T7
When q = - 1 / 2, T9

The food chain is formed by living things for the sake of other living things