The first year of junior high school Summer Vacation Homework solves the equation urgently

, -1 to the power of 2003

x=4, algebraic formula: 2001

y=3, z=3, and the value is 0

4.The left side of the first step is wrong.

x-1/2=5(2x+3)+6

x=-43/18

Downstairs, you got the last step of the last question wrong.

x=-17/31

x=-58/7

3.-5/12x=-11/12

x=11/5

x=-12/7

I'll do it for you.

Substituting x=1 to get it.

m 2 = m = 5 substitution m = 5 to obtain.

Because (m2-1) x 2-(m+1)x+8=0 is a one-dimensional equation, m=+1

So 2x=8

x=4 x+2]+[y-3]=0

So x=-2, y=3

Substituting (-8+z) 2=-1 2-5+z

4+5+1/2=z/2

3/2=z/2

z=3 substituting 3 2-9=0

1) Start wrong.

Solution: Remove the denominator to get: 2x-1=10(2x+3)+12 (1) Remove the parentheses to get: 2x-1=20x+30+12

Move the items and merge the same kind of items to obtain: -18x=43

The coefficient is reduced to 1, and x=-18 43 is obtained

Solution: a(x-1)>x+1-2*a

a-1)x>a+1-2*a

Because the set of solutions for x is x<-1

x<(a+1-2*a)/(a-1)=-1

i.e. (a+1-2*a) (a-1)=-1 and a-1<0 gives a<1

Subtract the two formulas to obtain x-y=1 x=y+1 and substitute one of the formulas: 1997y+1997y=1995, and the solution gives y=1

So x=2

1997x - 1999y=1995（1）1996x - 1998y=1994（2）（1）-（2）

1997x - 1999y=1995]-[1996x - 1998y=1994]

x-y=1]

Because x-y=1

So x=y+1

Substituting x=y+1 into (1) obtains.

1997y+1997-1999y=19951997-2y=1995

y=1, so x=y+1=2

1. Set this number x, move it one place to the right, and it becomes 10x just have: 10x-x= push x=

2. Cone volume: v1= cylindrical volume: v2= obtained from v1 v2, h1 h2 = 9

3. System of equations: the first bag: x, the second bag: y x=96 y=73

4. Former male employees: 630* Recruit x male employees, just have: (126+x) (630+x)= x=90

1.A shopping mall held a prize sales activity, each customer can participate in a certain amount of money after spending a certain amount of money**, the award number is a four-digit number composed of six numbers from 1 to 6, and the award regulations are as follows: First prize:

The number is 6666; 2nd Prize: x333; Third prize: xx22; Fourth Prize:

The last digit of the number is an even number.

Q: The probabilities of the first, second, third and fourth prizes are (1 1296), (1 216), (1 36), and 1 3 respectively

2.Psychologists have found that under normal circumstances, students' attention changes with the change of the teacher's lecture time, the student's attention gradually increases at the beginning of the lecture, and the student's attention remains in a more ideal state for a period of time in the middle, and then the student's attention begins to be scattered

Question: (1) From the table, after the lecture starts, the students' attention starts to decline from a few minutes? Guess that attention decreases during Y vs. T

and expressed in formulas.

Let this function be: y=kt+b, and substituting the values of time and attention gives this function as y=-7t+380

2) Using the relation in question (1), find what is the value of the student's attention y when t is equal to 27 points. There is an existing math problem that needs to be explained for 20 minutes, and in order to achieve better results, the students' attention span is required to reach a minimum of 190, so whether the teacher can finish the problem when the students' attention reaches the required state is the reason.

Question supplement: Class time t (points): 0 5 10 15 20 25 30 35 40 45

Student's attention y: 100 191 240 240 240 205 170 135

2) Answer: According to y=-7t+380, it can be concluded that when t=27, y=191

Yes, as you can see from the table, the attention span from 5 minutes to 25 minutes is above 190. Therefore, the question can be completed in 20 minutes.

Analysis, (1) First Prize, 1 6*1 6*1 6*1 6=1 1296 Second Prize, 1 6*1 6*1 6=1 216 Third Prize, 1 6*1 6=1 36

The fourth prize, since four are selected from 1 to 6 to form a four-digit number, then this number is either an odd number or an even number [the odd and even method is to look at the number at the end], therefore, the probability is 1 2.

2), 20 minutes later, it starts to decline, y=240-35*(t-20) 5

240-7t+140

380-7t，（45≥t≥20）

When t=27, 191.

Students are required to pay attention to a minimum of 190 and listen to the math problem in twenty minutes.

According to the chart, it can be seen that when t=5, the student's attention is 191, and when t=27, the student's attention is also 190, when 520, summary: [As long as the teacher starts to speak after 5 minutes of class, the requirements can be satisfied. Therefore, the teacher can finish the question with the student's attention at the desired level.

The four-digit number composed of six numbers to 6 has a total of: 6*6*6*6=1296, and the probability of the first prize is: 1 1296

The probability of the second prize is: 6 1296 = 1 216

The probability of the third prize is: 1 36

The probability of the fourth prize is: 1 3

6 to the 4th power 6 to the 3rd power 6 to the 2nd power 1 2

20 minutes y=minus 7x+380 Bringing t into y=191 Yes, there are 20 minutes from the fifth minute of class to the end of the 25th minute. I hope I can help you, choose me.

Is this a question from the first year of junior high school? I'm also a first-year junior high school student, so how can I feel so difficult?

1. 2(y-x）=3（x-y） (1)

3(x-4）=4（y+3) (2)

5(x-y)=0 from (1), i.e. x=y (3) and (2) get 4y-3x=-24 (4).

Substituting (3) into the spring stool belt (4) obtains: x=y =-242 2x+1=3y (1)

4x-9y=8. (2)

2)-(1)*2 is sold roughly: -3y=10, that is, y=-10 3 substitutes y=-10 reed 3 into (1) to obtain: x=-11 2

Solution: The distance from B to Lighthouse C is 30 nautical miles.

Rationale: At 8 a.m., a boat departed from point A and sailed due north at a speed of 15 nautical miles to arrive at point B at 10 a.m.

ab = 15 * 2 = 30 nautical miles.

nbc=∠nac+∠c,∠nac=42° ∠nbc=84°∴∠c=nac=42º

bc = ab = 30 (nautical miles).

The team will answer for you.

1.There are X people in class A, y people in class B, and z people in class C.

x+y+z=162

5/6-12=y

2/3y+17=z

The solution is x=55, y=54, z=53

A: There are 55 students in Class A, 54 in Class B, and 53 in Class C.

2.Efficiency of team A: 1 16=1 16 Efficiency of team B: 1 24=1 241 24*5=5 24

5 8-5 24) (1 16 + 1 24) = 4 (hours) Answer: 5 8 of the whole project can be completed by doing it for another 4 hours.

3.226*70%=RMB).

Set the purchase price of x yuan.

x=140 A: The purchase price of the product is 140 yuan.

I'm really tired of coding words, I'm sorry. Ask someone else. ^_

4. Set the speed of A to x and the speed of B to y

There are 6+2 3x=2 3y

3/2x+x=y

The solution is x=6 y=15

Distance: s=6+2 3x=2 3y=10km

5. Set up the car to travel for x hours, then the boat travels (x+3) hours 24 (x+3) + 40 = 40x

The solution yields x=7h x+3=10h

S male = 40 * 7 = 280km S water = 280-40 = 240km