Math problems in the first year of junior high school, urgent!!

Solution: Set the purchase price to be X yuan per piece.

Then there is an equation according to the meaning of the topic:

x130%×

Solution: x=1000

A: The purchase price is 1000 yuan.

Set the price of x yuan to earn 13% profit.

Then there is an equation according to the meaning of the topic:

Solution: x=1260

Answer: When the price should be 1260 yuan, you can earn 13% of the profit.

1) Let the purchase price be x yuan, then the list price is 130% of the purchase price, that is, 130% x, and the selling price is 90% of the list price, that is, 130% multiplied by 90% multiplied by x profit is the selling price The purchase price = 130% multiplied by 90% times x x The equation is 130% * 90% * x — x = 170x = 1000

2) Set the price of y yuan to earn 13% of the profit, then the selling price is (90% y - 4) yuan, and the profit is the selling price of the purchase price = 90% y - 4 - 1000

Then there is an equation according to the meaning of the topic:

90%y—4—1000=1000 13%solution: y=1260

1.Solution: Set the purchase price of each piece x yuan, according to the meaning of the question:

Solve this equation to get:

x=1000

2.Solution: Set the price to be marked at x yuan, according to the meaning of the question:

Solve this equation to get:

x=1260

1.Let the input price be x, then there is the equation: x* to solve the value of x.

The total length of the 60-knot chain is centimeters before installation.

Starting with the second chain, the diameter of the overlapping circles is reduced for each length, a total of centimeters.

So the total length of the chain after installation is 150 - = cm.

d 102cm

The total length of the chain = cm.

The total length of the 60-knot chain is centimeters before installation.

The length of the first two chains is reduced by a total of centimeters by the diameter of the circle that crosses the overlapping parts, so that the total length of the chain after installation is 102 centimeters.

（1）8500+7200+9100+7300+8200+8900=49200

8000*6 = 48000, so the total number of 6 teams completed reaches the required number.

2) 500 + (8500-8000) * 10 - (8000-7200) * 8 + 500 + (9100-8000) * 10 - (8000-7300) * 8 + 500 + (8200-8000) * 10 + 500 + (8900-8000) * 10 = self-calculation.

zhtkevin1, hello:

Solution: Let A bring 7x yuan, and B bring 6x yuan.

7x－50）：（6x－60）＝3：2

14x－100＝18x－180

4x＝80x＝20

A remaining: 7 20 50 90 (yuan).

B remaining: 6 20 60 60 (yuan).

If A brings 7x yuan, then B 6x

7x-50) :6x-60) = 3 :2 to get x=20

So left. 90 and 60....

1.Solution: Set x days to complete.

x/15+(x-7)/12=1

Multiply 60 at the same time to get :

4x+5(x-7)=60

4x+5x-35=60

9x=95x=95/9

A: 95 9 days to complete.

2.Solution: Set up x number of students.

240+240x÷2=240×

240+120x=144（x+1)

240+120x=144x+144

144x-120x=240-144

24x=96

x=4A: There are 4 students.

3.Solution: Set the original side length x cm.

According to the title, the side length of the truncated small square is (x-50) 2 cm 50 50 (x-50) 2 = 25000

x-50)/2=10

x-50=20

x=70A: The original side length is 70 cm.

4) My brother and my mother set off from home to go to my grandmother's house together, if my brother and my mother travel 2 kilometers per hour, then they need 1 hour and 45 minutes to get to my grandmother's house, after they have walked for 1 hour, my brother finds that the gift for my grandmother is forgotten at home, so he takes the gift and chases it at a speed of 6 kilometers per hour, can my brother catch up with my brother and mother before they go to my grandmother's house, why?

1 hour 45 minutes = hours.

Solution: Solution: When the elder brother catches up with the younger brother and the mother, the younger brother and the mother walk for x hours (6-2) * (x-1) = 2

4(x-1)=2

x-1=x=so I can catch up.

1.Set x days to complete.

x/15+(x-7)/12=1

4x+5x-35=60

9x=95x=95/9

2.When the number of students is x, the two travel agencies charge the same amount.

1+x/2=

1+x=43.Let the length of the original square iron sheet be x cm.

50*50*(x-50)/2=25000

x-50=20

x=70

Solution:1It takes x days to complete.

A does 1 15 of the whole work every day, and B does 1 12;

then there is 1 15 * x + 1 12 *(x-7)=1=>x=95 9;

2.If the number of students is x, the same amount will be charged;

Then there is 240+240 * x=(x+1)*240*=> x=4

3.Box height: 25000 (50*50)=10cm;

Therefore, the length of the cut square is 10cm

So the original square becomes 50+10+10=70cm

1 solution: Let it take x days to complete, get: x 15 + (x-7) 12 = 1 = > x = 95 9

2 solution: When students bring x people, A and B travel agencies charge the same amount, and they get:

240+120x=240*

x = 43 solution: 50 + 2 * open root number (25000 50 50) = 70

Solution (1) is set to be completed in a total of x days, and the column equation x 15 x-7) 12 = 1 is solved to obtain x=95 9

2) Suppose: There are a total of x students, and the equation 240+x240 50%=(x+1) 240 60% is solved to obtain x=4

3) Let the side length of the truncated small square be x cm, and the column equation 50 50 x=25000 is solved x=10, so the side length of the original square iron sheet = 50 + 10 2 = 70 (cm).

4) Let's set: It took x hours for my brother to catch up, and the equation 6x 2x=2 1 was solved to get x= At this time, my brother and my mother walked together 15 hours, less than 1 hour and 45 minutes, so be able to catch up with them.

1: 4011 part 2005*2+1=4011

2: The second question is unclear.

1 All Question 8: Question 1: 3x(1-2%)+4xx2%, 3(1000-x)(1-2%)+5(1000-x)x2%.

Second question: y=

Question 3: If y=3029, then x=550 students, 550 elementary school students, 450 junior high school students.

A township decided to provide nutrition subsidies to primary and junior high school students at the standard of 3 yuan per student per day, of which the subsidy standard for students with family difficulties is: 4 yuan per day for primary school students, 5 yuan per day for junior high school students, and it is known that there are 1,000 primary and junior high school students in the township, and 2% of the students in primary and junior high schools are boarding students with family difficulties.

The township has existing primary school students.

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1.If the polynomial (quadratic of x + cubic of x + 2x to the power of -3x+2) - (quadratic of ax - quadratic of 3x + bx + 1) does not contain the cubic term of x and the term x, find the value of algebraic equation 2 (quadratic of a + quadratic of ab+b)-3 (quadratic of -3ab-a). [I can't play the fourth power of x, so I'll use words instead of trouble you two].

x∧4+x∧3+2x∧2-3x+2）-（ax∧3-3x∧2+bx+1）

x∧4+x∧3+2x∧2-3x+2- ax∧3+3x∧2-bx-1

x∧4+（1-a）x∧3+5x∧2-（3+b）x+1

Cubic and x terms without x.

then 1-a 0, 3+b 0

then a 1, b -3

2（a∧2+ab+b∧2）-3（-3ab-a∧2）

a∧2+ab+b∧2+9 ab+3a∧2

4a∧2+10ab+b∧2

2.It is known that the quadratic of a=2x +3xy-2x-1 and the quadratic of b=-x +xy-1

1) Find 3a+6b

3a+6b＝3（2x∧2+3xy-2x-1）+6（-x∧2+xy-1）

6x∧2+9xy-6x-3-6x∧2+6xy-6

15xy-6x-9

2) If the value of 3a+6b is not related to x, find the value of y.

3a+6b＝15xy-6x-9＝（15y-6）x-9

Because it has nothing to do with x.

Then 15y-6 0

y＝2/53.Known |m-n-2|The square of (mn-1) is the opposite of each other, and the value of (-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn) is found.

m-n-2|＝-mn-1）∧2

Then: m-n-2 0, mn-1 0

2mn+2m+3n）-（3mn+2n-2m）-（m+4n+mn）

2mn+2m+3n-3mn-2n+2m- m-4n-mn

2+2-1）m+（3-2-4）n+（-2-3-1）mn

3m-3n-6mn

3（m-n）-6mn

3（m-n-2+2）-6（mn-1+1）

3（m-n-2）+6-6（mn-1）-6

3（m-n-2）-6（mn-1）

1.(x4+ x3 +2x2 -3x+2)-(ax3-3x2 +bx+1)

x4+（1-a）x3+5x2-(3+b)x+1

If the polynomial does not contain the cubic term of x and the term x, then 1-a=3+b=0, a=1 ; b= -3

2（a2+ab+b2）-3（-3ab-a2）=14-24=-10

b=-x2+xy-1

1) 3a+6b=15xy-6x-9=3(5xy-2x-3)

2) The value of 3a+6b is independent of x, 3a+6b = 15xy-6x-9 = 3x(5y-2)-9

Therefore, 5y-2=0, y=2 5

3. |m-n-2|and (mn-1)2 are inverses to each other, then |m-n-2|=（mn-1）2=0

m-n-2=0

mn-1=0

2mn+2m+3n）-（3mn+2n-2m）-（m+4n+mn）=--6mn+3m-3n

6mn+3（m-n）

0 look at it, right...

1. Merging similar terms, it can be seen that the known formula = x 4 + (1-a) x 3 + (2 + 3) x 2 + (-3-b) x + 1

Because it does not contain the cubic term and the x term, the coefficient 1-a=0 can be obtained according to the coefficient; -3-b=0

The solution is a=1; b=-3

So the equation is =2*(1-3+9)-3*(9-1).

2. It is known that the quadratic of a=2x + 3xy-2x-1, and the quadratic of b=-x +xy-1

1) Find 3a+6b

2) If the value of 3a+6b is not related to x, find the value of y.

1），3a+6b=15xy-6x-9

2) Take y as a constant, merge similar terms, and get.

3a+6b=15xy-6x-9=（15y-6）x-9

Because the value of 3a+6b has nothing to do with x, the coefficient of x must be 0, that is, 15y-6=0, and the solution is y=2 5

3.Known |m-n-2|The square of (mn-1) is the opposite of each other, and the value of (-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn) is found.

Because |m-n-2|Greater than or equal to zero, (mn-1) is greater than or equal to zero, and is the opposite of each other.

So |m-n-2|+(mn-1) is 0 squared, so |m-n-2|=（mn-1）=0

m-n=2(1),mn=1(2)

1) Convert to m=2+n, bring in (2).

Get n 2 + 2 n - 1 = 0

Solve n -1 root number 2

m corresponds to 2 root number 2