Given X & # 178; + x = 1, find the value of X & # 179; + 2x & # 178; = 891 2. Proof: for any natural number n, the value of n (n + 5) - (n-3) (n + 2) can be divided by 6

Given X & # 178; + x = 1, find the value of X & # 179; + 2x & # 178; = 891 2. Proof: for any natural number n, the value of n (n + 5) - (n-3) (n + 2) can be divided by 6

∵x²+x=1
∴x²+x-1=0
x³+2x²+891
=x(x²+x-1)+x²+x+891
=x(x²+x-1)+(x²+x-1)+892
=0+0+892
=892

4（x-2）²-25=0

4（x-2）²-25=0
4（x-2）²=25
（x-2）²=25/4
x-2=±5/2
x=2±5/2
X = 9 / 2 or x = - 1 / 2

For the same two liter bottle of beverage, Aunt Li bought a bottle of 5.05 yuan, while Aunt Zhang bought a bottle of 5.05 yuan
It's 6.40 yuan, but if you buy three bottles, you get one free. Please calculate. They each buy four bottles. Who's the best buy? (two methods)

Li: 5.05 × 4 = 20.2 yuan
Zhang: 6.40 × 3 = 19.2 yuan
Aunt Zhang is a good buy

New concept English for young people
What are the key points and grammar of the following paragraphs
That's OK.
I‘m saving money on the suit .
So now I want to buy a pair of shoes to go with it.
The teacher asked the students to talk about this natural passage by themselves!

That's OK is an oral sentence pattern
What do I save money on
So conjunction now time adverbial I want must add to conjunction verb to go with it

A. The distance between B and B is 80 kilometers. A bus starts from a to B, and a car starts from a to B in 2 hours. The speed of the car is three times that of the bus. As a result, the car arrives at B 40 minutes earlier than the bus

Let the bus speed be x, the car speed be 3x, and the bus time be y
yx=3x（y-2-40/60）
yx=80
There are two types of virtue
x=20km/h
3x=60km/h

If a root of the equation x ^ 2 + ax + B = 0 and x ^ 2 + BX + a = 0 (a is not equal to b) are the same, find the root

Let the same root be X
By subtracting the two equations, we get: (a-b) x = (a-b)
x=1

A. The distance between two places is 950 meters. Party A and Party B start from place a at the same time for 30 minutes. Party A walks 40 meters per minute and Party B runs 150 meters per minute
Ask a and B when they met the nearest to B. please use primary school method to answer, please write the process
The correct answer is a total of three encounters. The second encounter is closest to B, 150 kilometers away from B. I want an explanation, offering a reward of 50 points

Because only 30 minutes of exercise, and B walk faster, then B can walk 150x30 / 1900 = 2.3, that is to say, can walk two back and forth
If two people want to meet, they must take at least one round trip, and then a single trip
So from (40 + 150) x30 = 5700, 5700 / 950 = 6, then the two people can meet five times at most. The time is 10,15,20,25,30 minutes respectively
At this time, the distance a took was 40060080010001200,
Among the four numbers, 1000 is the closest to 950, so it should be the 25th minute. When they meet, they are the closest to B
If we meet three times, it is equivalent to abandoning the two times of B catching up with a, which is what I call the second and fourth times. Then we can only meet three times, and the smallest is the second time: 950-800 = 150

(x + 8) / 0.2 - (x-3) / 0.5 = 2 + (0.2x + 0.7) / 0.01

Multiply both sides of the equation by 1
5（x+8）-（x-3）=2+10（0.2x+0.7）
5x+40-x+3=2+2x+7
4x+43=2x+9
2x=-34
x=-17

A and B go in one direction. A starts at 12 noon, B starts at 2 pm. How far is it from the starting point when B catches up with a

Let B use time X
3*2+x*3=5*x
2x=6
X = 3 hours
The distance is
3*5=15

What's the number on the 2011 place after the decimal point after 9 / 14?

Because 9 / 14 = 0.6428571428571
So we use 428571 as a cycle
Because (2011-1) / 6 = 335, there is no remainder, so the number in 2011 is exactly 1