Let m = {x | x is greater than or equal to - 4}, n = {x | x is less than 6}, then the union of M and u is equal to () A {x | - 4 less than or equal to x less than 6} B-null set C {x | - 4 less than or equal to x less than or equal to 6} D real number set Please tell me the steps. I want to know the solution

Let m = {x | x is greater than or equal to - 4}, n = {x | x is less than 6}, then the union of M and u is equal to () A {x | - 4 less than or equal to x less than 6} B-null set C {x | - 4 less than or equal to x less than or equal to 6} D real number set Please tell me the steps. I want to know the solution

Landlord, it should be the union of M and n
The concept of union is a set of all elements in two sets
X ≥ - 4 refers to all real numbers greater than or equal to - 4
X ≤ 6 refers to all real numbers less than or equal to 6
The combination of the two is all real numbers, so choose D
I suggest you draw the solution set of M and N on the draft paper, and it will be clear

Triangle ABC is an equilateral triangle, D is a point outside the triangle ABC, connecting ad, BD, DC, and the angle BDC = 120 degrees

Certification:
Extend BD to point e so that de = DC,
∵∠ BDC = 120 degrees, so ∠ CDE = 60 degrees
The ∧ CDE is an equilateral triangle
 ∠ ECD = 60 degrees, CD = CE
∵∠ BCE = ∠ ACD, and △ ABC is an equilateral triangle, AC = BC,
∴ACD≌△BCE
∴AD=BE=BD+DE=BD+DC

The dimension of linear space formed by all second-order matrices over real number field R, and a set of bases are given?

It's very simple. The dimension is four
Ji, just take it like this (typing out definitely can't submit, too many numbers)
Doesn't a matrix of order 2 have four elements?
One element is taken as 1, and the other elements are taken as 0. There are four such second-order matrices, which are his bases
Similarly, you can define the dimension of M * n matrix as Mn, and the definition of base is similar

The angle between a straight line and a plane
In the pyramid p-abcd, the bottom surface ABCD is rectangular, PA ⊥ plane ABCD, PA = 5, ab = 4, ad = 3. Find the angle between the line PC and the plane ABCD

Since the vertical plane of PA is ABCD, the angle PCA is the required angle
According to Pythagorean theorem, AC = 5
So in the triangle PAC, PA = AC = 5 and angle PAC = 90
So PCA = 45

Find the definite integral of the square of SiNx from 0 to π, and an original function of the square of SiNx!

Wait a moment, and the picture solution will come out;
Click to enlarge, then click to enlarge

Translation: what is the center of this article is this sentence --

What's the main meaning of this passage?

The square of x minus 7x plus 6 equals 0,

x²-7x+6=0
(x-1)×(x-6)=0
x1=1 x2=6
How to explain? The factorization of the original equation is the second step

Area formula of rectangle Square Letter

S=ab
S=a^2

Let f (x) be an odd function defined on R, and if x is greater than zero, f (x) = 1 + 2 to the x power, then the value of F (- log23) is equal to

The answer is - 4

Ask math questions (to calculate the process)
3 2
Given that | A-4 | and | a + 2B | are opposite to each other, find the algebraic formula 10 (a-b) - 8 (a-b) + 9 (b)
3 2
A) + 7 (B-A)
Because of typing, the power has been moved to the front. Note: after each bracket, there is a power: 2

|A-4 | and | a + 2A | are all numbers greater than or equal to zero, so they are all zero, and a = 4, B = - 2
Original formula = 180