Seek understanding!!!! How to distinguish between math problems

4m-a 0,m is a positive integer solution of 1 2 3 4Find the value of a: 4 a, 8 a, 12 a, and 16 a

4m-a 0, when the positive integer solution of m is 1, when 4 a is 2, 8 a

For 3 hours, 12 a

Question 1 A can be equal to 4m Question 2 A must be greater than 4m

Proof: ab=ac

ABC is an isosceles triangle.

abc=∠acb

dg parallel ac

gdf=∠aed

DFG = CFE (equal to the apex angle).

acb=∠aed+∠cfe

Because acb= abc

abc=∠aed+∠cfe

dgb=∠gdf+∠dfg

abc=∠dgb

So DGB is an isosceles triangle.

db=dgdb=ce

dg=EC2 has (1) easy proof.

DGF congruent triangle CFE

aas）fd=fe

1.There are 22 boys and 23 girls in a class, and the number of boys is 22 23 of the number of girls, and the unit "1" here is the total number of girls, and the number of boys is 22 45 of the total number of students in the class, and the unit "1" here is the total number of students in the class.

2.Cut a piece of cake into 4 pieces, Xiao Ming ate one of them, and there was 3/4 of the cake left(The reason is that it is not necessarily divided into four equal portions when cutting).

3.Three-quarters of a meter is as long as one-quarter of a three-meter. (

4.In order to establish the class book corner, Wang Ming donated one-fifth of his collection, Li Xing donated four-fifths of his collection, and Wang Ming donated more books. (The reason for this is that they are all based on their own collections.)"1", the number of books in the collection is uncertain, so there is no comparison)

5.In the 2012 London Olympic Games, the Chinese delegation ranked second in the medal table with 38 gold, 27 silver and 23 bronze medals. The number of silver medals in our country is 27 88 out of the total number of medals, and the number of bronze medals is 23 88 out of the total number of medals

I hope it helps, and I wish you progress in your studies!

22 23 Girls 22 22+23=22 45 The class was wrong because he didn't say it was the average.

False, because unit 1 is different.

22 23 Number of girls 22 45 Class size.

Wrong, right. False 27 88 23 88

When a is not equal to zero, the unary quadratic equation under the root number should be greater than or equal to zero under the root number, so the unary quadratic equation should open upwards and have at most one intersection point with the x-axis, so b 2-4ac is less than or equal to 0 and is expected to be adopted.

Because the number of squares to be opened is in the form of a quadratic function, in order to be greater than 0 constantly, it should be opened upward, so a>0, and there is no intersection with the x-axis, then <0

Because f(5)=f(1)=-5 was calculated earlier, so replace f(5) in [] with -5, and the period is four, then f(-5) should be equal to -f(5), f(-1)=-f(1), you can replace f(-5)=f(-1), and then go back to the title to see the given formula, and bring the number in (

Read the question carefully.

We have already calculated that f(x+4)=f(x).

So f(-5) can be understood as when x=-5 (x+4 is equal to -1), so the above equation can be replaced by f(-5)=f(-1)

Substituting the formula given in the question, f(-1)=1 f(1) is known to be f(1)=-5, so f(-5)=f(-1)=1 f(1)=-1 5

f f ( 5) The value of f (5) has been obtained in the previous step as - 5, and f (-5) = f ( -5 + 4) = f ( 1) , and f ( x ) = 1 ( x +2) can be obtained from the previous step, so f ( 1) = 1 f ( 1 ) = - 1 5

There is a problem that can only be with a period of four, because f5 = -5 soff5 f (-5 for).

The first question.

The second question. This should be right, I haven't done math in a long time.

1What is the 4-hour downwind flight of all aircraft when the windless speed is a kilometer and the wind speed is 20 kilometers?

4（a+20）

What is the 3-hour flight of an airplane against the wind?

3(a-20)

What is the difference between the two trips?

4(a+20)-3(a-20)=4a+80-3a+60=a+140

The 4-hour trip of the aircraft downwind = 4 (a + 20) = 4a + 80

The flight of the aircraft against the wind for 3 hours = 3 (A-20) = 3A-60

4a+80-（3a-60）=a+140

The downwind stroke is 4*(A+20); The headwind stroke is 3* (A-20).

The difference between the two is 4*(a+20)-3*(a-20)=a+140

From the question setting, it can be seen that s=vt, then:

Downwind flight s1=4(20+a);

Flying against the wind s2=3(a-20);

Stroke difference s=s1-s2=140+a;