If {denotes a new operation symbol, and a {B = (a + b) / (a-b), then (72 {56)} 6=（ In this paper, we define a new operation symbol and specify a ∞ B = (a + b) / (a-b), then (72 ☆ 56) ☆ 6 = () what number should be filled in the registration,

（72☆56）☆6
=[(72+56)/(72-56)]☆6
=8☆6
=(8+6)/(8-6)
=14/2
=7

In this paper, a new symbol of operation is given, which is called "2 + 3 + 4", 7 ﹥ 2 = 7 + 8, 3 ﹥ 5 = 3 + 4 + 5 + 6 + 7. According to this rule, 10 ﹤ 4=______ .

10◎4
=10+11+12+13
=46
So the answer is: 46

&It is known that 2 & 3 = 2 + 3 + 4; 7 & 2 = 7 + 8; 3 & 5 = 3 + 4 + 5 + 6 + 7

A & B = a + (a + 1) + (a + 2) +... (a + B-1) there are B terms including a
Take the above questions for example
2&3=2+（2+1）+ （2+3-1）=2+3+4
7&2=7+ （7+2-1）=7+8
3&5=3+（3+1）+（3+2）+（3+3）+ (3+5-1)=3+4+5+6+7
So 5 & 8 = 5 + (5 + 1) + (5 + 2) + (5 + 3) + (5 + 4) + (5 + 5) + (5 + 6) + (5 + 8-1)
=5+6+7+8+9+10+11+12 =68

Suppose a and B are rational numbers, and the meaning of the sign "is a * b = | a | + (- 6), try to find the value of (- 2) * 5

Minus 3

Let AB be all rational numbers, and the meaning of sign x is that a times b equals 4AB, 2x6 equals 4x2x6 = 48 If no matter what number x is, there will always be a times x = X

3 times - 5 = 4 × 3 × (- 5) = - 60
A times x = 4 × a × x = 4ax = x, then 4A = 1, a = 1 / 4

Let a and B be rational numbers, and the meaning of the sign "△" is: a △ B = (a + b) - (a-b), and find 3 △ (- 5)

a △ b = (a+b)-(a-b) 3△（-5）=3+（-5）-[3-（-5）] =3-5-8 =-10

Let a and B be rational numbers, specify the meaning of sign * a * b = - A-B, and find (- 2 * - 3) * - 4)

=（2+3）*（-4）=-5+4=-1

Algorithm of permutation and combination? Use 1,2,3,4,5 to arrange randomly. The numbers can be repeated, but the sum must be equal to 15, How many permutations are there? I arranged with Excel, the answer is 381, this is a stupid way, who knows how to calculate with formula?

First of all, let's assume that it's a five digit array each time?
It can be considered in the case of repetition and non repetition
No repetition is a complete arrangement of five numbers, with 120 kinds;
There are 120 / 4 = 30 kinds arranged by 1, 1, 3, 5 and 5;
There are 120 / 4 = 30 kinds arranged by 1, 1, 4, 4 and 5;
There are 120 / 4 = 30 kinds arranged by 1, 2, 2, 5 and 5;
There are 120 / 6 = 20 kinds arranged by 1, 2, 4, 4 and 4;
There are 120 / 6 = 20 kinds arranged by 1,3,3,3,5;
There are 120 / 4 = 30 kinds arranged by 1, 3, 3, 4 and 4;
There are 120 / 6 = 20 kinds arranged by 2, 2, 2, 4 and 5;
There are 120 / 4 = 30 kinds arranged by 2, 2, 3, 3 and 5;
There are 120 / 4 = 30 kinds arranged by 2, 2, 3, 4 and 4;
There are 120 / 6 = 20 kinds arranged by 2, 3, 3, 3 and 4;
There is one sort of arrangement of numbers 3, 3, 3, 3
So there are 381 species

The Organizing Committee of the 2010 Guangzhou Asian Games will select four volunteers from Xiaozhang, Xiaozhao, Xiaoli, Xiaoluo and Xiaowang to be engaged in translation, tour guide, etiquette and driver respectively. If Xiaozhang and Xiaozhao can only do the first two jobs, and the other three can do these four jobs, then there are different selection schemes () A. 36 species B. 12 species C. 18 species D. 48 species

According to the meaning of the topic, it can be divided into two situations,
① If Xiao Zhang or Xiao Zhao were selected, c21c21a33 = 24;
② If both Xiao Zhang and Xiao Zhao are selected, the selection method a22a32 = 12,
There are 36 kinds of selection methods,
Therefore, a

A permutation and combination problem 60 pieces of different pieces, put into 30 squares, a grid can only put one piece, how many ways to put it?

This kind of problem is considered on one side. Consider according to the lattice
The first grid has 60 ways to put, the second grid is the way to have the remaining pieces
Down in turn. The 30th grid is the rest of the pieces, that is, 31 ways to put
So it's 60 * 59 * *31 = 60! / 30!. (! Is factorial)

If {denotes a new operation symbol, and a {B = (a + b) / (a-b), then (72 {56)} 6=（ In this paper, we define a new operation symbol and specify a ∞ B = (a + b) / (a-b), then (72 ☆ 56) ☆ 6 = () what number should be filled in the registration,