There are math problems about the first year of junior high school! Kneel and beg!! Kneel down and b

as-5>2s-2a

s(a-2)>5-2a

The first case: when a>2, s>(5-2a) (a-2) because s>-1

So. 5-2a)/(a-2)=<-1

Get a>=3

The second case: when a<2

s<(5-2a)/(a-2)

So there is no such a thing as -13.

The third case:

a=22s-5>2s-4

The equation does not hold.

Comprehensive situation 1 and

Get a>=3

AS-5 2S-2A AS-2S 5-2A S(a-2) 5-2aa 2, S (5-2A) (A-2) (5-2A) (A-2) -1 A 3

a 2, s (5-2a) (a-2) (5-2a) (a-2) (a-2) >1 a<2

When a=2, 0>1 is not true.

aScope {a|A<2 or A3}

as-5>2s-2a, collated to get a(s+2)>2s+5, because s -1 so s+2>1 , is a positive number, so a>(2s+5) (s+2).

2s+5) (s+2) =2+1 (s+2), s>-1, s+2>1, so 1 (s+2)<1, so a>=3

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.

Let the value of ax 3+bx-5 of the polynomial stove rock be 2 when x=2, then the value of ax 3+bx+15 is found when the implicit match x=-2.

3+bx+15

x=-2 is considered a sell-out.

x2.The second question is to bring in the whole thing.

2a^3+2b-5=2

2a^3+2b=7

When the ant is late and teases x=-2, ax 3+bx+15=-(2a 3+2b)+15=-7+15=8

I'm also a freshman in junior high school, so I hope I can help you!

If the number of people was x, it is now 2x

6000/x-10800/(2x)=20

6000/x-5400/x=20

600/x=20

x=30A: The original number of people was 30.

The original ** was 6000 30 = 200 yuan, and now it is 200-20 = 180 total savings: 20 * 60 = 1200 yuan.

(1) There are x people who are scheduled to participate in the training.

6000/x=10800/(2x)+20

6000/x=5400/x+20

6000=5400+20xx=30

10800 (6000*2)=10800 12000=9 10=9% discount after the number of people increases.

6000*2-10800=12000-10800=1200 After the discount, it saves a total of 1200 yuan compared with the non-discount.

The number of people who were originally scheduled to participate in the training was x.

Saved 2*6000-10800=1200

Average savings per person 20=1200 2x

x=30, so it should cost 6000 per person, 30=200

The first question was learned) to save 20 per person

Enjoyed a 9% discount, saving 20 yuan compared with no discount.

Assuming that there were x people, it was originally planned that x people would use 6,000 yuan, and later 2x people would use 10,800 yuan, indicating that x people would use 5,400 yuan later. 6000-5400 = 600, and each person uses 20 yuan less than the original plan, 600 20 = 30 people.

10800 60 = 180 yuan.

6000 30 = 200 yuan.

So it was a nine-percent discount, saving 1,200 yuan compared to the original.

Set up person x, the original cost per person is 6000 x, and enjoy the y discount, then the discount is 600y x per person

600y x ·2x=10800 y=9 So after 9 discounts, a total of 6000 ·2-10800 = 1200 yuan is saved after 9 discounts, and the average per person is 20 yuan less after 9 discounts, then the 1 discount saved is the 20 yuan ** for 20, and the original number of people is 6000 200 = 30 people.

(1) Set up, the original x people to participate in the training.

6000/x-10800/2x=20

Solution: x=30

2) The ** without discount should be 12000, and the total savings after the discount are 12000-10800=1200 compared with the non-discount

10800 12000=, so 9% off.

Listing an equation and assuming that the number of people is x, then there is:

1200/x-20=10800/（2x）

x is equal to 30 The second question should not need to be talked about, the answer is 9% off, each person saves 20 yuan, a total of 1200

This problem requires an equation, and if there are x people who are scheduled to participate in the training, then.

6000／x-10800／2x=20

It's done.

Connect CB, angle DCB+DBC=90°-32°-21°=37°

148 ° + 37 ° = 185 ° (unqualified because the ideal state of the inner angle of the triangle and the state is 180 °, should not be 148 °, should be 180-37 = 143 °).

Solution: (1) Set up B and C cooperation to complete the task in x days.

1/12＋1/20）×4＋（1/20＋1/15）x＝18/15＋7x/60＝1

7x/60＝7/15

x 44 4 8 (days).

2) 180 (1 80) 100 (yuan) 100 (1 30) 130 (yuan).

A: The maximum counteroffer for this kind of product is 130 yuan.

1. Let the width be x, then:

x+28) 2=46 (your perimeter data here is incorrect, correct)2,x=5 Substituting the equation to get a=2

3,120 x and (x-10) 2 = 2x-20120 x = 2x-20

The solution is x=25, and the test is correct.

4. Both sides of the equation can only be divided by non-zero numbers at the same time, and the solution of this equation is 0, and all three students are wrong.

5, Let the middle of these three numbers be x, then x2+x+x+2=96 solves x=32, so Xiaohua gets 30 32 34 Let these four cards be x-6 x-4 x-2 x sum is: 4x-12 It is obvious that it is a multiple of 4, 213 does not match, assuming the sum is 212, then: 4x-12 = 212 x=56

The smallest number is 56-6=50