Given that the set a = {x ∈ n | 86 − x ∈ n}, the set a is represented by enumeration=______ ．

Given that the set a = {x ∈ n | 86 − x ∈ n}, the set a is represented by enumeration=______ ．

From the meaning of the question, we can see that 6-x is a positive divisor of 8, when 6-x = 1, x = 5; when 6-x = 2, x = 4; when 6-x = 4, x = 2; when 6-x = 8, x = - 2; and X ≥ 0, ｜ x = 2, 4, 5, that is, a = {2, 4, 5}

In △ ABC, A2 + C2 = 2B2, where a, B and C are the side lengths of angles a, B and C respectively. (1) prove that B ≤ π 3; (2) if B = π 4 and a is an obtuse angle, find a

(1) From the cosine theorem, CoSb = A2 + C2 − b22ac = A2 + c24ac (3 points) because A2 + C2 ≥ 2Ac, CoSb ≥ 12 (6 points) & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; from 0 < B < π, we get & nbsp; & nbsp; B ≤ π 3, and prove the proposition (7 points) (2) sine from

Help me to work out a math problem of grade 6, give 300 points to the right one, and write down the steps of the formula
For a piece of iron wire, two fifths of its total length will be used for the first time, and 14 meters for the second time. The ratio of the remaining one to the used one is 1:3?
The speed ratio of car a and car B is 5:8. The two cars start from a and B at the same time and meet at 24 kilometers away from the midpoint. How many kilometers are there between the two places?

1. Let the wire be x meters long
3/4x=2/5x+14
7／20x=14
x=40
40×1/4=10(m)
A: there are still 10 meters left on this wire
2.8-5 = 3 (speed difference)
24 × 2 = 48 (km) (distance difference)
48 △ 3 = 16 (travel time)
16 × (8 + 5) = 208 (km)
A: A and B are 208 kilometers apart

Take any three numbers from 1-5 to form repeatable permutation numbers. How many combinations are there?
RT, note that the numbers can be repeated

5 zones and 3 zones are arranged and combined, and the order of consideration is 5x 4x 3 = 60

Given that f (x) is an odd function defined on R and satisfies f (x + 2) = - f (x), f (1) = 2, then the value of F (2011)

f(2011)=f(2*1005+1)=-f(1)=-2.

Party A and Party B process a batch of parts at the same time. It is known that the work efficiency ratio of Party A and Party B is 3:2. Party A goes out for a meeting for two days in the middle of the process, and when it is finished, Party A processes half of this batch of parts?

Party A can complete 1 / 2 of the time, and Party B can complete:
1/2×2/3=1/3
A out of 2 days, B completed: 1 / 2-1 / 3 = 1 / 6
B efficiency: 1 / 6 △ 2 = 1 / 12
Efficiency: 1 / 12 × 3 / 2 = 1 / 8
It takes 1 / 8 = 8 days for a to complete alone

What line's focus is the center of the triangle?

1. The height of the three sides of the perpendicular triangle intersects at a point, which is called the perpendicular center of the triangle. 2. The center line of the three sides of the gravity triangle intersects at a point, which is called the center of gravity of the triangle. 3. The middle perpendicular of the three sides of the triangle intersects at a point, which is called the center of the circumscribed circle of the triangle

Let a, B, C ∈ R, a + B + C equal o, ABC > 0, prove 1 / A + 1 / B + 1 / C
Another question: compare the quartic power of 1 + 2x with the square of 2x + the square of X?

a+b+c>0
So there are positives and negatives
Let a > = b > = C
abc>0
So one positive and two negative
a>0>b>=c
1/a+1/b+1/c=(bc+ac+ab)/abc
abc>0
Looking at molecules
a+b+c=0
a=-(b+c)
So molecule = BC + a (B + C)
=bc-(b+c)²
=bc-b²-2bc-c²
=-(b²+bc+c²)
=-[(b+c/2)²+c²/4]=2x³+x²

How to use derivative and definite integral to solve calculus? Derivative and definite integral are the core concepts of calculus. What is the relationship between them?
It's better to be more detailed

Calculus is divided into differential and integral, and differential is derivative, that is to say, function f (x) differentiable at x = a is equivalent to Differentiable here. There is no direct connection between derivative and definite integral, but derivative and indefinite integral are closely related. Derivative and indefinite integral are inverse operations, while indefinite integral and definite integral are connected by Newton Leibniz formula

How many four digit numbers can be composed of 0, 1, 2, 3, 4 and 5, which are greater than 3000 and less than 5421?

3 × 5 × 4 × 3-2 × 3 = 174
Mathematical permutation
For the four digits of a number greater than 3000, the thousand digits can be 3, 4 and 5, and the hundred digits can be 6. If you don't repeat, you have to subtract the selected one of the thousand digits to be 5. And so on, the ten digits can be 4, the single digits can be 3, and the multiplication can be more than 3000
Similarly, if the number is greater than or equal to 5421, 5 and 4 of thousands of digits are the largest. Considering the number of tens and ones, you can choose 2 and 3, 2 × 3, respectively
Subtract the two