1. Chengbei primary school has three extracurricular groups: the science and Technology Group has 10 people, accounting for 20% of the total number of the three groups. The ratio of the number of literature and art groups and sports groups is 3:1. How many people are there in the sports group? How many people are there in the literature and art group? 2. In ancient times, the height of a big tree was usually measured by the shadow of a big tree. There was a man whose height was 1.8 meters, and his shadow length was 2.88 meters. At the same time and at the same place, the shadow length of a tree was 12 meters. How many meters was the height of the tree?

1. Chengbei primary school has three extracurricular groups: the science and Technology Group has 10 people, accounting for 20% of the total number of the three groups. The ratio of the number of literature and art groups and sports groups is 3:1. How many people are there in the sports group? How many people are there in the literature and art group? 2. In ancient times, the height of a big tree was usually measured by the shadow of a big tree. There was a man whose height was 1.8 meters, and his shadow length was 2.88 meters. At the same time and at the same place, the shadow length of a tree was 12 meters. How many meters was the height of the tree?

All = 10 △ 20% = 50
Sports group = (50-10) / (3 + 1) × 3 = 30
Art group = 50-10-30 = 10 people
Tree height = 12 × (2.88 △ 1.8) = 19.2m

What does the center of gravity of a triangle mean

The center of gravity of a triangle is the intersection of its three midlines
Theorem of center of gravity: the three middle lines of a triangle intersect at a point. The distance from this point to the vertex is twice the distance from it to the midpoint of the opposite side. This point is called the center of gravity of the triangle

For the quadratic trinomial x2-20x + 36, Xiao Cong made the following conclusion: no matter what real number x takes, its value cannot be equal to 11
Do you agree with him? Give your reasons

x²-20x+36=(x-36)(x+4)
x²-20x+36=11
x²-20x+25=0
x²-20x+100=75
(x-10)²=75
x=10±5√3
Rational numbers and irrational numbers are called real numbers, and (10 ± 5 √ 3) is a real number

Is f '(1 / x) = DF (1 / x) / DX?
Can it be understood as f '(1 / x) * DX = f (1 / x)? Why?

Should be DF (1 / x) / D1 / X

N + 1 n-dimensional vectors must be related. N-dimensional vectors are uncertain. What about n-1 n-dimensional vectors?

When the number of vectors does not exceed the dimension, it is uncertain

A problem of solving second derivative by differential of implicit function
X ^ 2 + 3Y ^ 2 = 5 to find the second derivative, namely d2y / DX2
I can only find the first dy / DX = - X / 3Y, and then how can I further derive this equation?

d2y/dx2=-1/3*[Y-Xdy/dx]/Y^2=-(y+x^2/3y)/3y^2

Let f (x) be second-order differentiable. Find the second-order derivative of the following function y = f (x ^ 5)

Y '= (5x &;) f' (X &;) y '' = 20x & ³ f '(X &;) + (25X &;) f' '(X &;) if I can't see the number of times clearly, I rewrite y' = (5x &;) f '(x ^ 5) y' '= 20x &; f' (x ^ 5) + (25X ^ 8) f '' (x ^ 5) hope it can help you. If it solves the problem, please click

The numerator of 1993 / 1992 minus a number and the denominator plus this number, the score is 2 / 3, and this number is ()

Let the number of addition be X
(1992-x)/(1993+x)=2/3
x=398

General solution of differential equation y "'- 3Y" + 2Y' = 0
Please tell me the formula of the root of the characteristic equation and the corresponding term of the general solution of the differential equation

The characteristic equation of Y "'- 3Y" + 2Y' = 0: R ^ 3-3r ^ 2 + 2R = 0: r = 0,1,2
y=C1+C2e^x+C3e^(2x)
Note: higher order is the same as second order

What is M & # 178; + 2Mn + n & # 178; divided into M & # 178; - N & # 178?

M-178; + 2Mn + n-178; divided into m-178; - n-178;
=(M + n) & (M + n) (m-n)
=M-N of M + n