How many sets of a, B, C satisfy a ∪ B ∪ C = {1,2,3,4} The answer is to the fourth power of seven

How many sets of a, B, C satisfy a ∪ B ∪ C = {1,2,3,4} The answer is to the fourth power of seven

There are 81 kinds of the fourth power of 3. There is no such option. I'll tell you what I think, right? Can we think of this problem as the problem of putting the ball into practice? 1234 is like four balls, ABC is like three barrels, and each ball can be put into ABC's three barrels at will, that is, there are three methods, so it's the fourth power of 3

Let u = R, a = {x | - 1 ≤ x ≤ 3}, B = {x | - 0}

　　（1）A∩B={x|0＜x≤3},A∪B={x|-1≤x＜4}；
(2) when a ∈ (3,4), (C ∪ a) ∩ B = (0, a);
When a ≥ 4, (C ∪ a) ∩ B = (0,4);
（3）a≥4；

What is the meaning of the eloquent Tao

Tao has no practical meaning here. Its meaning is the same as saying
It's flexible, responsive and eloquent

Idioms with tongue 1: to describe eloquence 2: to describe not well——
.

1: Description is eloquent
2: Not good at description

From a through B to C is an asphalt road, from a through D to C is a small road, people walk from a to C, often take the small road instead of the asphalt road. Why not take the asphalt road, but like to take the small road? Please explain the reason with what you have learned

As shown in the figure, extending the intersection of AD and BC to e, according to the trilateral relationship of triangle, AD + de < AB + be, CD < de + CE, so, AD + CD < AB + BC, so, people don't take asphalt road, but like to take small road

Tortoise and rabbit race, from a to C, tortoise runs ①, rabbit runs ②. Do they run the same length of two routes? Why?

② The length of the route is: π× (6 + 4) △ 2 = 5 π ① the length of the route is: π × 6 △ 2 + π × 4 △ 2 = 5 π, so the lengths of the two routes are the same. Answer: the lengths of the two routes they run are the same

Use DAO to form a word with different meanings: A, B, direction, method, C, D, technology and skill（
Use DAO to form a word with different meanings: A, B, direction, method, C, D, technology, skill

A street

C language C = (a ^ b)

A and B do XOR operation first, then shift two bits to the left, and finally assign value to C

a-a = a ×c -b× c= a -b× 2=
A-A = a × C - B × C = a - B × 2 = this is the fifth grade equation. First answer, first offer

0,c（a-b）,a-2b

What does a ∩ B ∩ C mean?

C should mean non-C. it is a set that contains all the elements in I except the elements in C