Find a one dimensional inequality problem, the more the better.

x-y=2k---1

x+3y=1-5k---2

1+2 gets: 2x+2y=1-3k

Because the sum of x and y is negative.

So 2(x+y)=0

1-3k=0

k=1/3

The first formula adds the second formula.

2x+2y=2k+4-5k=4-3k

According to the title, 4-3k is less than 0

Therefore k is greater than 4 3 haha.

It is known that x-2m>2x+4 do not have a positive integer solution, so find the range of the value of m.

A factory had 280 employees in the year before last, and last year after structural reform and reduced 40 people, the annual profit of the whole plant increased by 1 million yuan, and the per capita profit increased by at least 6,000 yuan.

When the quarry is blasted, after igniting the fuse, the worker should move to a safe area 400 meters away before blasting, the fuse burning speed is 1cm s, the speed of the worker transfer is 5m s, how many meters should the fuse be greater than?

Answer: The annual profit of the whole factory in the year before the establishment was x million yuan, x 280+

Solution x 308

The annual profit of the whole plant was at least 3.08 million yuan the year before last.

Solution: Set the fuse to be x meters.

x/>400

X>A: The fuse should be larger than the meter.

1.If you have to run for at least x minutes, there is a distance relationship:

90 (30 - x) +210x 3300, get x 5 so he has to run for at least 5 minutes.

2.Let this tens of digits x, the single digit be 2x, and it is easy to know that 1 x 4 has 0 10x + 2x - 36 36, and we get 3 x 6

So x can be equal to three or four, i.e. the numbers can be 36 and 48.

3.That inner angle is between 0° and 180°, so there is:

2250° n-2) 180° 2430° n so n = 15.

4.If the number of children is x, then the number of apples is 3x+8.

The second condition translates to that the number of apples is less than 5x, but greater than 5(x-1), so we get 5(x-1) 3x+8 5x, and we get 4 x

So x = 5, with five children, the number of apples is 3x+8 = 23.

Don't forget to add points, have fun!!

3-2x＞-1

x≥a 4＞2x

x＜2∴2＞x≥a

There are five integer solutions.

a=-22＞x≥-2

x＞1x＜0（2）-1≤1

21-x 2 or 1-x -2x -1 or x 3

2a+b-3c=1,(2)

1)-(2)*2: -a+7c=3, a=7c-3b=1-2a+3c=1-2(7c-3)+3c=-11c+7 due to a 0, b 0, c 0

7c-3≥0, c≥3/7

11c+7≥0, c≤7/11

3/7≤c≤7/11

m=3a+b-7c=3(7c-3)+(11c+7)-7c=3c-2When c=3 7, m has a minimum value: x=3*3 7-2=-5 7When c=7 11, m has a maximum: y=3*7 11-2=-1 11xy=-5 7 * 1 11)=5 77

In 2002, the number of days of air closure was 365*55%=201 days.

In 2008, the number of days of air *** needs to be 366*55%=

So at least an increase of 256-201 = 55 days.

Solution: If Satoshi answers x questions incorrectly, then Satoshi answers (19-x) correctly (19-x) questions with 5 (19-x)-2x>80

95-5x-2x>80

5x-2x>80-95

7x>-15

x<2 and one-seventh.

So Satoshi answered at most 2 questions incorrectly.

The landlord should be able to see it.

(20-x)*5-2x>80

7x<20

x<=2

So at most two questions are wrong!!

Satoshi can answer up to 2 questions incorrectly 5 (20-1-x)-2x>80

7x<15

x<2 and 1 7

Exclude it. If you can draw a graph of the exponential function, it is simpler to first d a>1 is impossible, as the exponent increases to the n power of a will be larger than a a is also impossible, in that case, as the exponent becomes larger, the n power of a will become smaller and smaller, and then look at b.

a<-1, then if the exponent of a is negative, then the nth power of a is also negative, understand?

And a<-1, the bigger the exponent, the smaller it is, for example, a=-10, a3 is -1000, and 5 is -100000

So a 7 Then, a <-1, a absolute value must be greater than 1

Then A2 is greater than A

A 4 is greater than A 2