People's education press primary school sixth grade volume two Chinese unit 1 test paper composition how to write? A chicken is teaching a duck to draw bamboo leaves. The chicken is very similar to the duck, but the duck is like the leaves. The chicken is angry and the duck is crying. The chicken says that the duck has been learning for a long time, and even the bamboo leaves can't be drawn

People's education press primary school sixth grade volume two Chinese unit 1 test paper composition how to write? A chicken is teaching a duck to draw bamboo leaves. The chicken is very similar to the duck, but the duck is like the leaves. The chicken is angry and the duck is crying. The chicken says that the duck has been learning for a long time, and even the bamboo leaves can't be drawn

Write your own feelings: chickens should not be so rude, they should teach ducks in simple terms, and then associate with the reality of life (ask again if you don't understand)

Examples of balance in life! A little more!

(1) When people stand still on the ground, gravity and the supporting force of the ground are a pair of balance forces;
(2) When a crane lifts a heavy object at a constant speed, the gravity of the heavy object and the tension of the crane's wire rope on it are a pair of balance forces

The difference between 5x times x minus 3 is the sum of x minus 3 times x plus 1
Ask God to reply

5x*(x-3)=(x-3)*(x+1)
If x = 3, the formula is true but meaningless
If x ≠ 3
Then divide both sides by x-3 & nbsp; to get
5x=x+1
x=1/4

Find the value of 4xy - [x ^ y - (2xy-2x ^ y) + XY] - 2x ^ 2
It is known that - 2A ^ x + 1b ^ 4 and 3a ^ 2B ^ 2 are similar

It is known that - 2A ^ x + 1b ^ 4 and 3a ^ 2B ^ 2 are similar
x+1=2
y+2=4
We get x = 1, y = 2
4xy-[x^y-(2xy-2x^y)+xy]-2x^2
=5xy-3x^y-2x^2
=10-3-2
=5

What are the advantages of mechanical calculator over abacus?
After reading the article about curta calculator, I thought of abacus. When I asked an engineering child what's the difference between the two, his answer was: it's cool to look at. Abacus can also carry out four operations, and it can also be accurate decimal places. So I feel that this small and exquisite Kurt calculator has no advantage. Please give me some advice

Abacus is not popular in the international market. However, there is one thing that calculators can never match. Abacus can be used as a skateboard
Hope to adopt

Change X & # 178; - 2x + 2010 into general form

(x-1)²+2009

Let the sum of the first n terms of the sequence an be Sn = 4 / 3an-1 / 3 * 2n + 1 + 2 / 3, n = 1,2,3 .
(1) Find the first term A1 and the general term an;
(2) Let TN = 2n / Sn, n = 1,2,3 It is proved that ∑ ti

When n = 1, A1 = S1 = (4 / 3) A1 - (1 / 3) * 2 ^ (1 + 1) + 2 / 3 = (4 / 3) A1-2 / 3, the solution is: A1 = 2;
When n > 1:
Sn=(4/3)an-(1/3)*2^(n+1)+2/3=(4/3)an-2*(1/3)*2^n+2/3
S(n-1)=(4/3)a(n-1)-(1/3)*2^n+2/3=(4/3)a(n-1)-1*(1/3)*2^n+2/3
an
=Sn-S(n-1)
=[(4/3)an-2*(1/3)*2^n+2/3]-[(4/3)a(n-1)-1*(1/3)*2^n+2/3]
=(4/3)an-(4/3)a(n-1)-(1/3)*2^n
∴(1/3)an=(4/3)a(n-1)+(1/3)*2^n
That is, an = 4 * a (n-1) + 2 ^ n
4*a(n-1)=4^2*a(n-2)+4*2^(n-1)
……
4^(n-2)*a2=4^(n-1)*a1+4^(n-2)*2^2
By adding the above formulas, we can get the following results:
an=4^(n-1)*a1+2^n+4*2^(n-1)+… +4^(n-2)*2^2
=2^(2n-2)*2+2^n+2^2*2^(n-1)+… +2^(2n-4)*2^2
=2^(2n-1)+2^n+2^(n+1)+… +2^(2n-2)
=2^(2n-1)+2^n[2^0+2^1+… +2^(n-2)]
=2^(2n-1)+2^n*2^0*[1-2^(n-1)]/(1-2)
=2^(2n-1)+2^n*[2^(n-1)-1]
=2^(2n-1)+2^(2n-1)-2^n
=2^1*2^(2n-1)-2^n
=2^(2n)-2^n
∵ A1 = 2 = 2 ^ 2-2 ^ 1, in line with the above formula
The general formula of {an} is an = 2 ^ (2n) - 2 ^ n
(2) Certification:
Sn=(2^2-2^1)+(2^4-2^2)+… +[2^(2n)-2^n]
=[2^2+2^4+… +2^(2n)]-(2^1+2^2+… +2^n)
=4[1-(2^2)^n]/(1-2^2)-2(1-2^n)/(1-2)
=(4/3)[(2^n)^2-1]-2(2^n-1)
=(4/3)*(2^n)^2-4/3-2*2^n+2
=(4/3)*(2^n)^2-2*2^n+2/3
Then TN = 2 ^ n / Sn = 1 / [(4 / 3) * (2 ^ n) - 2 + 2 / (3 * 2 ^ n)] = (3 / 2) * 1 / (2 * 2 ^ n + 1 / 2 ^ n-3)
Let f (n) = 1 / (2 * 2 ^ n + 1 / 2 ^ n-3)
=(2^n)/[2*(2^n)^2+1-3*(2^n)]
=(2^n)/(2^n-1)(2*2^n-1)
=[(2*2^n-1)-(2^n-1)]/(2^n-1)(2*2^n-1)
=1/(2^n-1)-1/[2^(n+1)-1]
Then TN = (3 / 2) * f (n) = (3 / 2) * {1 / (2 ^ n-1) - 1 / [2 ^ (n + 1) - 1]}
∴n
∑ Ti=T1+T2+T3+… +Tn
i=1
=(3/2)*{(1-1/3)+(1/3-1/7)+(1/7-1/15)+… 1/(2^n-1)-1/[2^(n+1)-1]}
=(3/2)*{1-1/[2^(n+1)-1]}
=3/2-(3/2)*{1/[2^(n+1)-1]}

It is known that the absolute value of a is greater than 1 and that of B is greater than 1. It is proved that the absolute value of 1-ab is greater than that of a-b
Such as the title

To prove | 1-ab | > | A-B |, we should prove (1-ab) ^ 2 > (a-b) ^ 2. (1-ab) ^ 2 - (a-b) ^ 2 = (a ^ 2-1) (b ^ 2-1) > 0

If the area of triangle ABC is (a square + b square - C Square) / 4, then what is COSC equal to?

S△ABC=(a^2+b^2-c^2）/4
c^2=a^2+b^2-2ab*cosC
S△ABC=2ab*cosC/4=(1/2)*ab*cosC
S△ABC=(1/2)*ab*sinC
cosC=sinC=√2/2

Using dichotomy to design an algorithm to solve the approximate value of equation x3-2 = 0 on [1,2]

X3—2=0
【1,2】
Is it the third power of X?
#include
#include
#include
int main()
{
double low=1,high=2,mid;
int test=100;
while(test--)
{
mid=(low+high)/2;

if(mid*mid*mid