Those who can do math and calculate problems will advance, and those who will be able to solve math

1. x=1

Under the root (1-x) + under the root (x-1) + x square - 1 = 02In the same way, a = 1

b=0 a+b=±1

3.Under the root (111111-222) = 111 under the root (1001-2) = 111 * 111 * 9 under the root

Under the root (11...) 1-22。。。2) = 111111 (n) * 33333... 3 (n 3).

i、 0ii、 5

iii. If there is a problem with the subject of the building, it should be under the root (1111-22) 33 to see the number of rules 1 and the number of 2.

The first 2a, 1 a, 1 b, 2 b, 1 1, 3, the second, 4a, 1 a, 1 b, 2 b, 2, 3, 3, 3, 6a, 1 3b, 1 3, 3

The fourth (counted) 8a, 1, 4b, 2, 4, 3

Push it. nth 2n 1 n b n 3

1)1-x≥0，x-1≥0

So x=1(1-x)+x-1)+x2-1=0+0+1-1=0a2-1 0,1-a2 0

So a1=-1, a2=1

So b1=b2=4;

a+b = 3 or 5

3) It should be.

It allows you to observe the first three equations, and allows you to refer to them to generalize.

But it's okay to do that"{}"represents the number of repetitions).

1. x=1

b=0 a+b=±1

3.Under the root (111111-222) = 111 under the root (1001-2) = 111 * 111 * 9 under the root

Under the root (11...) 1-22。。。2) = 111111 (n) * 33333... 3 (n 3).

The first two questions are to find the size according to the defined field in the root number.

There are explanations before, so I won't talk about it.

Or 5 is mostly what you need to know about 111....1 (n 1) (10 n-1) 9 11....1,2n 1 formation is (10 2n-1) 92....

2, (n 2) 2* 111....1 (n 1) can be transformed into is, 2*(10 n-1) 9

Subtraction, (10 2n-2*10 n+1) 9=(10 n-1) 2 9 open arithmetic root, which is (10 n-1) 3 3(10 n-1) 9 i.e., 333....3 (n 3).

The first question is x=1, so the result is 1.

Question 2 a=-1 or 1 brings in b=4 a+b=5 only then does it make sense under the radical).

The third question is a simple inference, what is the process.

1。Because 1-x 0 x 1

x-1≥0 x≥1

So x=1 under the root (1-x) + under the root (x-1) + x square - 1=02In the same way, a = 1

b=0a+b=±1

3.Under the root (111111-222) = 111 under the root (1001-2) = 111 * 111 * 9 under the root

Under the root (11...) 1-22。。。2) = 111111 (n) * 33333... 3 (n 3).

To make. Root (1-x) + root (x-1) + x square-1 makes sense, then.

x=1so. Original = 0

Id. a+b=5

11...1 (2n) - 22....2 (n) 11....

1 (2n) - 11....1 (n) - 11....1 (n) - 11....

100...0 (n 1s, n 0s)-11....1 (n) - 11....

1 (n) * 100....0 (n 0)-11....1 (n) - 11....

1 (n)*9....9 (n).

11...1 (n) square*9

33...3 parties.

Basketball: 45*60%=27 (pcs).

Volleyball: 45-27=18 (pcs).

After selling a batch of basketballs, volleyball accounted for (1-25%) of the total, so now there are 18 (1-25%) = 24 (pcs) for basketball and volleyball

45-24=21 (pcs).

Pick me! I was right! o( o haha.

After selling, volleyball accounted for 75%, there were 18 volleyballs, and a total of 18 were left, and 21 were sold.

At the beginning there was one in basketball.

So there are 18 volleyballs.

In this question, the number of volleyballs should be grasped unchanged, 45*60%=27 (pieces) 45-27=18 (pieces), and there are 18 volleyballs. After selling, volleyball accounts for 1-25% = 75% of the current game, there are 18 volleyballs, 18 divided by 75% = 24 (pieces), the current total is 24, 45-24 = 21 (pieces), and 21 basketballs are sold.

a =210 , b=90

Calculation: a b = 7 4

a+70/b+70=7/4

Find the above equation to get the value.

Let a be 7x then b is 3x

7x+70）:（3x+70）=7:4

28x+280=21x+490

28x-21x=490-280

7x=210

x=30A: A is 210 yuan B is 90 yuan.

Let a be x, then b is 3 7(x).

x+70)/(3/7(x)+70)=7/44x+280=3x+490

x=2103/7(x)＝90

The original **A of the two commodities was 210 and B was 90

Let the ** of a and b be 7x and 3x

7x+70：3x+70=7:4

7(3x+70)=4(7x+70)

21x+490=28x+280

7x=-210

x=30a=7*30=210 b=3*30=90

Saline contains salt.

18 20 kg).

Now the salt water is heavy.

kg) need to be added with water.

30 18 12 (kg).

The salt content is 18*20%=

The diluted solution is:

30-18=12kg

Add 12kg of water

Use 18 kilograms by 20%, that is, the grams of table salt are grams.

If you need to mix 12% salt water, that is, you need 30 grams of water.

Then 30-18, that is, 12 kg of water needs to be added.

The answer is: 12 (grams).

Let the velocity x in the still water and the velocity of the water flow y

Therefore 105 (x+y) +60 (x-y) = 9 in the same way 84 (x+y) +75 (x-y) = 9 gives x=6y, y=3, x=18

Let the velocity x in the still water and the velocity y of the water flow

It can be seen that the downstream velocity is x+y, and the countercurrent velocity is x-y

Columnable equations: 105 (x+y)+60(x-y)=984 (x+y)+75(x-y)=9

Find x=18 y=3

Radius of the bottom surface of the bucket r=diameter 2=d 2=20 2=10cm

Bucket bottom area s= r2 =

v=s*h(height of ascent)=

The bottom surface diameter is 20cm

Base area s=100 square centimeters.

It is not very clear whether it rose to 15 cm or 15 cm.

So I'm divided into two types.

If it rises to 15 cm, then v=300 cubic centimeters.

If it rises by 15 cm, then v=1500 cubic centimeters.

The principle is that the volume of water discharged is the volume of this billet.

There are x people in the class.

x/4+12)/x = 50%

x/4 +12 = x/2

x/4 =12

x = 48 Answer: There are 48 students in the class.

Autumn Wind Yanyan answers the question o( o

If you don't understand anything, you can continue to ask this question.

If you are satisfied, please select the satisfactory answer in time, thank you.

The ratio of the number of people who went this Saturday to the class was 1:3

The number of people who went this Saturday was 1 4 = 25% of the class

This time, 50% of the class attended

It is known that 12 students went to this Sunday, accounting for the total class size (50%-25%)=25%, and the six (1) classes totaled 12 25%=48 students.

As everyone went out to work, Class 6 (1) students took the initiative to use the weekend to help the elderly in the village with the housework they could, and the ratio of the number of people they went to this Saturday was 1

1：200=25：x x=5000

1:200=y:2500 y=

219:21=x:189 x=171 Because the areas are equal, the volume ratio = the higher ratio.

1.(1) 5000 (1:200=25: water = 25x200 1=5000 kg).

2) (1:200=Medicine: 2500 Medicine=1x2500 200=kg.)

2.171cm (19:21=Cuboid: 189 189x19 21=171cm).

Multiply by 200 = 5000 (kg) 2500 divided by 200 = 1250 (kg).

Divide by 19=s s times 21=answer.