A very good math problem, a very novice math problem.

It cannot be replaced by a union symbol.

Because functions are not monotonically decreasing over an entire area.

Let's say f(-1) so you can't say the subtraction function over the entire definition domain.

But both intervals are subtractive functions.

Of course! The function is perfect in the interval (- 0), (0, + is a subtraction function" and "the function is a subtraction function on (- 0)u(0, +".

Equivalent statement.

No, monotonically decreasing on the two intervals (- 0), (0, +, respectively, but if it is denoted by (- 0)u(0,+, it means monotonically decreasing over the entire defined domain, by the function image, this is obviously not right, -1 1, the corresponding y(-1) is also less than y(1), this is not right, understand?

No, because u means that these two intervals are considered as a whole, obviously when the value of the function at x>0 is larger than at x<0, it does not meet the definition of a subtraction function, and the comma indicates that the function is a subtraction function in these two intervals, and the two intervals are considered separately, so it cannot.

The function at 0 is a breakpoint, discontinuous, and there is no point in discussing increment and decrease.

An important purpose of discussing the increase and decrease of continuous functions is to use it to solve equations using trial algorithms. It's still impossible to calculate.

No, with the symbol (- 0)u(0,+ are all subtraction functions, i.e., there is a single subtraction in the whole definition, but in fact it is a single subtraction in two intervals, such as x=1, y=k, but x=, -k

No.. Using u means (- 0)u(0,+ is a complete interval, but taking x=-1 and x=2 in this interval tells us that it is increasing. So the two intervals should be written separately.

Yes, because x is not equal to 0, it means that it is equivalent to the union of these two defined domains, and you didn't pay attention to the lecture in class? Huh

No, because the inverse proportional function doesn't make sense at x=0, and the limits are not equal at x=0, and you'll understand the limits later when you learn the middle limits of higher numbers.

It cannot be described as a subtraction function The meaning of the ton number is that both intervals meet the requirements.

Looking down, the answers upstairs and downstairs seem to be contradictory.

From the angle a:angle b:angle c=1:1:2, this triangle form isosceles right triangle, so a=b, so c 2=a 2 + b 2=2b 2 choose d

I don't understand......I'm only in the fifth grade, eh......

Solving Differential Equations:

1. 6x-[6y√(x²+1)](dy/dx)=0

Solution: Separate the variable ydy=xdx (x +1).

i.e. ydy=(1 2)d(x +1) (x +1).

Take the integral y 2=(1 4) (x +1)+c 2

Therefore, y =(1 2) (x +1)+c is the general solution of the equation.

2. du/dt=e^( u(0)=1

Solution: Separate the variable [e (

i.e. there is (1

The e of the integral (

t=0 when u=1, so there is e; c=e^

Therefore, it is specially interpreted as e (

i.e. u=(1

3. 7yy′=x y(0)=11

Solution: 7ydy=xdx (7 2)y=x 2+7c 2;Therefore there is y = x 7+c

When x=0, y=11, so c=121, that is, y =x 7+121 is its special solution.

4 [x²/(y²-6)](dy/dx)=1/2y y(1)=√7

Solution: Separate the variable 2ydy (y -6)=dx x i.e. d(y -6) (y -6)=dx x

The result of the integral ln(y -6)=-1 x+c; Therefore y = e (-1 x+c)+6

x = 1 when y = 7Substituting yields 7=e (-1+c)+6;1=e^(-1+c)；∴c=1

Therefore, it is explained as y = e [(1 x)+1]+6=e (1-1 x)+6

Your question should be: 10 million tons of oil a year, or it does not correspond to the actual situation. Here's the answer:

40 million people = 40000000 people (plus four zeros), 1000 tons = 1000000 kg (plus three zeros) = 2000000 jin (multiplied by 2), with 2000000 40000000 = jin.

A: The average person consumes catties of oil per year.

Jin = 2,250,000 kg (divided by 2) = 2,250 tons (remove three zeros) Answer: 90 million people use 2,250 tons of oil a year.

1000 tons = 10 3 tons = 10 6 kg = 2 * 10 6 catties.

40 million people = 4 * 10 7 people.

2*10 6 kg 4*10 7 people = kg person-years.

It is a serious oil shortage area.

Suppose Sichuan has a population of 90 million people who use oil a year.

9000 4000 1000 = 2500 tons.

The average person-year per person.

Average oil consumption per person = total oil consumption Number of population.

Total oil consumption = population * average oil consumption per person.

1 ton = 1000 kg.

1 kg = 2 catties.

1000 tons = 2000000 catties.

40 million = 40,000,000 people.

90,000,000 = 90,000,000 people.

The first section indicates that it takes 4 minutes and the journey is 3 kilometers, and the first section of the horizontal line does not increase the journey from the fifth minute, indicating that the car has stopped for one minute, and so on to know how much distance has been traveled in what time period.

So you can know that it takes 20 minutes to travel from station A to station D, and the journey is 10 kilometers.

So the first question takes 40 minutes to get from A to D round trip.

The distance from A to D is 10 km.

Average speed = total distance Total time = 10 km 20 minutes = 10 km (1 3 hours) = 30 km h.

Car trip, A->B, 4 minutes, 3 km, 2 minutes stop at B. B->C, 4 minutes, 2 km. Dock at C for 2 minutes.

C->D, 8 minutes, 5 km. It takes 20 minutes and covers a total of 10 kilometers.

Question 1: If a->d, return at the same speed, 40 minutes.

2: a- d, a total of 10 km.

3: a-d, average speed, 10 km 20 min = 30 km h.

A to B has a flat line that means stop for 2 minutes, the distance does not change, the answer is 20 minutes, 10km, kilometers per hour.

1. It takes 40 minutes to go back and forth.

2. The distance is 10 kilometers.

kilometers and hours.

This kind of problem is to understand the graph, in fact, it is very simple, that is, the ordinate represents the itinerary, and the abscissa is the time, as long as it is based on the graph.

Students between 70 and 95 are: 47-3 = 44 (person) 75-95 includes: 95-74 = 21 (number) points.

Average value per score: 44 21 = 2 (person) ......2 (people) No matter which score the remaining 2 people are, there will be 3 people in that value, so at least 3 people have the same score value.

You belong to the problem of the concept of the topic, and what you say is not unreasonable if you understand it literally, but if you think like this, it may be a drill, and mathematics is most afraid of this, because mathematics is actually a very rigorous thing, once you get into a dead end, you may feel that if you do a question in the future, it may be two answers if you understand it in two ways. Normal thinking is actually 3, don't think about this question for the time being, maybe tomorrow or when you eat, you will suddenly figure it out.

The answer is correct. For x=0, the value of 1 x is the limit value, and infinity, i.e., when the denominator is equal to zero, the fraction is not zero.

1 x = 0, i.e. when x is positive infinity, then lim1 x = 0 (i.e., the limit of x is 0, i.e. 1 x = 0).

The so-called limit theorists are not clear, the definition of 1 x in x is r is unlimited (x is not the same as x is not big), and there are times when the question or the teacher or the scope of learning is wrong.

This is a problem of finding the limit, and the limit of 1 x is equal to 0 when x approaches infinity

Original formula 3a-5 = 3+1

Add 5 on both sides at the same time

3a-5+5=3+1+5

In this case, -5+5 is calculated with the middle bracket first, and 0 is obtained

3a+（-5+5）=9

3a = 9 divided by 3 on both sides at the same time

3a÷3=9÷3a=3

Move 5 to the right of the equal sign, and say yes or no.

Well, maybe that's wrong???

So what???