A mathematical concept, ask a master to parse and parse it?

1) When the number of x is 0, 1, 5, 6, the period of change with the increase of n is 1, that is, it occurs every time, such as 6

6^1=6,6^2=36,6^3=216,..That is, the single digit is 6 consecutively, and as n increases, 6 appears on the single digit every time.

When the single digit of x is 4, 9 and the period is 2, it means that with the increase of n, 4 or 9 will appear in the number every other time, such as: 4 1 = 4, 4 2 = 16, 4 3 = 64 ,..It can be seen that when the single digit increases from 1 to 2 with n, the second digit will be.

A 4 appears once in the single digit

2) That is, no matter what x is equal to, as long as it is a positive integer, the single digit of his square number can only be the following five.

One of the numbers: 0, 1, 4, 5, 6, 9, e.g. 11 squared is 121, 12 squared is 144, 13 squared.

The square is 169, the square of 14 is 196, the square of 15 is 225....The single digits of these squares are nothing more than a list.

One of six numbers.

3) This is similar to (2), except that (2) is for the square of x, and here it is for the fourth power of x.

4) means that for any positive integer, the single digit of the product of his product with the number greater than 1 to him can only be

One of these three numbers. Such as 87*88 7656, 95*96 9120, 156*157 24492, 157*158

24806...There are always no more than these three digits in the single digits.

5) The single digit of the power to the left of the equal sign is the same as the single digit of the power to the right of the equal sign.

For example, if x=7 and n=1 are 96889010407 on the left and 40353607 on the right, then the number on the left and right is in the single digits.

The numbers are all 7

To find the single digit, simply multiply the single digit of the number.

1) The single digits of the number 0, 1, 5, 6 squares are 0 (0), 1 (1), 5 (25), 6 (36) and then multiplied by their own single digits or unchanged The single digits of the period of 1 4, the square of 9 are 6 (16), 1 (81), n = 3 when they are 4, 9 is the same as n = 1, and then the cycle is continuous, so when the period is 2 n = 2, the single digits of 2, 3, 7, 8 are 4, 9, 9, 4 n = 3, respectively 8, 7, 3, 2 n = 4, when they are 6, 1, 1, 6, and n=5 are 2, 3, 7, 8, respectively, which is the same as n=1, so the period is 4

2) The single digit of x is taken as 0......The last digit of 9 is 0,1,4,5,6,9

3) The single digit of the fourth power is equivalent to the single digit of the product of the square single digit (0,1,4,5,6,9), i.e. 0,1,5,6

4) Take 0...... for x single digits9 x + 1 single digit corresponds to 1, 2, 3 ......0 multiplied by single digit intelligence is 0, 2, 6

5) From (1) 4n is known as 0, 1, 2, 3 ,......The period of 9 (which is an integer multiple of 1,2,4) holds.

Hello, glad to answer for you! We can see that the rectangle of this big Nianfeng is made up of five layers of small rectangles, and it can be seen that the width of each small rectangle is 10 centimeters; Then look at the four layers in the middle, which is equivalent to the length of each rectangle, which is 40 centimeters, and finally the area of each rectangle is 400 square centimeters or meters. The answer is D.

1) (b) a), this does not need to be explained.

2) acb>0, then -a<-b<0, so c-ac-b "with thick 0

3) a>b, AC2BC2, need to consider the case of c=0.

4) This < does not need to be explained.

5) a|b|, so a b = a|/|b|>16) a>5,5-a<0,b<-5,Min Xing positive b+5 < 0 , the two negative numbers are multiplied, so (5-a)*(b+5) >0

1, less than or equal to, 2, less than, 3, greater than or equal to, 4, less than, 5, greater than, 6, greater than.

For the basic question type of junior high school, it is recommended to read the textbook several times.

The answer is that the Chang dry bird is empty and the following is the year of the hole.

Comparing sizes can be compared using the method of comparison, that is, using them as bad symbols.

a²-(2ab/3-b²)

a²-2ab/3+b²（1）

a-b/3)²+8b²/9

Because a, b are not 0 at the same time, so the above equation is greater than 0, so a >2ab 3 + b

In this case, formula (1) can also be regarded as a quadratic expression about a, and the judgment can be determined by using the discriminant beating book celebration style to grasp the judgment.

4b²/9-4b²≤0

And a, b are not 0 at the same time, so a > is 2ab 3 + b

a*a - 2ab/3 - b*b)

a*a -2ab/3 + b*b

a-b 3)(a-b 3) +8b*b 9 (1) So, a, b are not 0 at the same time, there must be (1) equation 0 so a*a > 2ab 3-b*b

a*a -2ab/3 + b*b

a*a - 2ab/3 +(b/3)*(b/3) -b/3)*(b/3)+ b*b

This is the commonly used method of serving and closing (a b)*(a b), which is to divide the coefficient of the ab term (this formula is -2 3) by 2, multiply by b, and then square. Add one of these numbers, and then subtract one of these numbers, and the original old laughing style remains unchanged.

Then the top three can match the above results.

Because a 2 -(2 finches 3ab-b 2) a -2 3ab+b is rented.

a-1/3b)²+8/9b²>0

So a 2 > dong 2 3ab-b 2

Let the radius of the Earth be r and the radius of the basketball be r

Then the length of the line of the earth = 2 r

String length of basketball = 2 r

The radius of the earth is larger than that of a basketball, so the line of the earth is long.

are elevated after 1cm.

The length of the Earth's line = 2 (r+1) increased by 2

The string length of the basketball = 2 (r+1) has been increased by 2

So both lines increase by the same amount.

This one... The longest circumference of the cross-section of a sphere is the circumference of its largest diameter circle, the equator of the earth and the largest cross-section of a basketball... Of course, the line at the equator of the earth is long...

Raising both lines is equivalent to an increase in the radius of the largest cross-sectional circle by 1 cm. If it is an absolute value, then both increase by the same amount, both are 2 centimeters, and if it is a percentage, then the basketball line increases by more percentage.

(1) The length of a loop of wire wrapped along the Earth's equator close to the ground.

2) Just as much.

The circumference of that circle at the equator = d centimeters.

The circumference of that circle of the basketball = d centimeters.

The diameter of both times has been increased by 1 cm.

This time: the circumference of the circle at the equator = d+1) = d + cm The circumference of the circle in basketball = d+1) = d + cm means that both have increased by centimeters.

So just as much!

First of all, it must be the length of the line of the earth, because the radius of the earth is as long as that of a basketball, so the circumference is also greater than that of a basketball.

When their radii are increased by 1 cm, that is, the increase in the circumference of the two lines that are too high by 1 cm (assuming r is the radius of the earth) = 2 (r+1) 2 r=2

The increase in the circumference of the basketball line (assuming r is the radius of the basketball) = 2 (r+1)-2 r=2

Since the circumference of the two wires increases by the same amount, they increase by the same amount.

Just as much.

The circumference of that circle at the equator = d centimeters.

The circumference of that circle of the basketball = d centimeters.

The diameter of both times has been increased by 1 cm.

This time: the circumference of the circle at the equator = d+1) = d + cm The circumference of the circle in basketball = d+1) = d + cm means that both have increased by centimeters.

It's definitely the antenna of basketball that has increased a lot.

f(x)=4x+ 9 (x-5)(x>5)4(x-5)+20+9 (x-5).

Rent + 12 + 20 32 minimum 32

x>4,x+ 1/(x-4)= x+4)-4+1/(x-4)=²2-4=-2≥-2

When the pie wheel (x-4) = 1 (x-4), there is a minimum value of -2, at which point x=5x>3

2x+ 1/（x-3）= 2(x-3)+6+1/(x-3) =2+6≥8

When (x-3)=1 (x-3) there is a minimum value of 8, at which point x=4

The question assumes a=b

The previous inferences are correct.

In the penultimate step 2(a-b)=a-b is actually 0=0 in the last step, since a-b=0, so both sides cannot be removed at the same time, and it is customary for the divisor [denominator] not to be 0.

So it's actually a mistake in the solver's algorithm that leads to the wrong conclusion.

It's okay to deceive elementary school students with this kind of thing.

2(a-b) = (a-b)

If a-b is not equal to 0, both sides can be divided by a-b at the same time

In the last step, 2(a-b)=a-b becomes 2=1, which is divided by a-b

At the same time, the premise of dividing a-b is a-b≠0, i.e., a≠b

But the first line is a=b, contradictory, and can't be divided by a-b, so it's wrong.

Hello in the penultimate row, since a=b, you can't divide a-b on both sides

Hope it helps.

Of course, this is not correct, you have already said a=b in the first step, then a-b=0, in the penultimate step 2(a-b)=a-b, the place cannot be divided by a-b on both sides (cannot be divided by a 0 at the same time), so the answer of 2=1 will not appear.

Haha, it's fun, the front is right, it's just that the last 2 1 is wrong. But I can't understand any science that is so unscientific.

The previous steps are all true, and the last step 2=1 is wrong, because: 2(a-b)=a-b pushes out 2=1, both sides are divided for (a-b) at the same time, and a-b=0, if the divisor is 0, it does not make sense.

So you can't push 2=1.

Broadly speaking, science is a subdisciplinary knowledge system that reflects the objective laws of nature, society, thinking, etc. The word "science" was first used by modern Japanese academics to translate the English word "science" and other corresponding words in European languages, and the word ** in European languages is derived from the Latin word "scientia", which means "knowledge" and "learning", and in modern times it focuses on the study of nature. The word science means "the study of the imperial examination" in ancient Chinese.

The Meiji era Japanese Enlightenment thinker Western Zhou used "science" as a translation of "science". In 1893, Kang Youwei introduced and used the word "science". Since then, the word "science" has been widely used in China.

Depend on! Since a=b, a-b=0, both sides of the equation cannot be divided by 0.

Science is science!

Hello, I'm going to try my best to help you solve this favorite problem:

Question 1: 2500 90%-100=2150 yuan. 2150 (1+RMB.)

Question 2: Set the purchase price as: X yuan. Then: (x 150%) 80%=x-160, solve the equation to obtain x=240 yuan.

Question 3: Set the price of 3,000 yuan for a simple leather coat with a maximum of x discount, then; The column equation yields: 3000x=2000 (1+5%), x=

Therefore, the price of the standard Qiqi is 3,000 yuan, and the leather clothing will be discounted by 7% at most.

I hope it can help you, I'm satisfied, thank you.

Select item A. Connecting ao, do proves that the triangle aod is similar to the triangle boe, then ad:be=ao:bo=root number 3:1