On the number axis, a point 5 units from the origin represents the number______ The absolute value is the number of itself______ ．

On the number axis, a point 5 units from the origin represents the number______ The absolute value is the number of itself______ ．

According to the geometric meaning of absolute value, we can know that the number represented by the point of 5 unit length from the origin on the number axis is the number with absolute value of 5, so the number is 5 or - 5, and the absolute value of positive number and 0 is itself, so you can fill in a non negative number, so the answer is: 5 or - 5; non negative number

On the number axis, the number represented by four points of unit length away from the origin is______ ．

According to the meaning of absolute value, the number represented by four points of unit length away from the origin is obtained, that is, the number whose absolute value is 4 is ± 4

How many points on the number axis are 4 and 1 / 2 unit length from the origin?

Two

On the system of equations of x.y {x + 4 = y + 3a, 2x-y = 2A, the solutions of which are opposite to each other, find the value of A

According to the meaning of the title:
x+y=0
x=-y
Substituting x = - y into the equations, we get the following results:
4-2y = 3A equation 1
-3Y = 2A equation 2
The deformation of equation 2 is as follows:
Y = (- 2 / 3) a equation 3
The results are as follows
y=-8/5
a=12/5
So a = 12 / 5

It is known that two straight lines L1: (3 + m) x + 4Y = 5-3m, l2:2x + (M + 5) y = 8. When m is different, 1) intersect, 2) parallel, 3) vertical
(2) If two lines are parallel, K1 = K2 is required
==> -(3+m)/4 = -2/(m+5)
==> m² + 8m +7 = 0
==>M = - 1 or M = - 7
But when m = - 1, the two linear equations are identical and the lines coincide
Therefore, when m = - 7, the two lines are parallel
L1：y=[5-3m－(3＋m)x]/4
How to get K1 = - (3 + m) / 4?

By using the point oblique formula y = KX + B

When two straight lines are known: L1: (3 + m) x + 4Y = 5-3m; L2: 2x + (5 + m) y = 8; what is the value of M, L1 intersects L2

When m = - 5, L2 is parallel to y-axis, L1 is not parallel to y-axis, L1 is not parallel to y-axis
When m-5
Then (3 + m) / 42 / (5 + m)
(m+3)(m+5)8
m^2+8m+158
(m+1)(m+7)0
M-1 and M-7
Then M is not equal to - 1 and not equal to - 7 L1 L2

It is known that three straight lines L1: 2x + (M + 3) y = 8, L2: (M + 1) x + 4Y = 11-3m, L3: x + Y-1 = 0. When what are the values of m respectively, L1, L2 and L3 are three non coincident lines intersecting at the same point?

2x+(m+3)y=8 1
（m+1）x+4y=11-3m 2
x+y-1=0 3
It seems that the system of quadratic equations with three variables can not be solved, but in fact it has some skills
By subtracting 1 from 2, we can get the following results
(m-1)x-(m-1)y=3-3m
(m-1)x-(m-1)y+3(m-1)=0
(m-1)(x-y+3)=0
Then M = 1 or X-Y = - 3
When m = 1, the lines L1 and L2 coincide
When X-Y = - 3:
x-y=-3
x+y-1=0
The solution is x = - 1, y = 2, and 1 (or 2) is brought in
So m = 2
So when m = 2, L1, L2 and L3 are three non coincident lines intersecting at the same point
If you don't understand, you can ask me again

In △ ABC, ab ≠ AC
A. Suppose ∠ B = ∠ C B. suppose ab ≠ AC, which one?

Proof: suppose ∠ B = ∠ C, AB / sinc = AC / SINB can be known from sine theorem, because ∠ B = ∠ C, SINB = sinc, so AB = AC is contradictory to known ab ≠ AC, so: ∠ B ≠ C (end of proof)

In straight triangular prism abc-a1b1c1
The length of side edge is root 2, and the bottom is an equilateral triangle with side length 1

The angle BC1D is the solution. Tanbc1d = two-thirds root sign three / two-thirds root sign seventeen, and then the inverse function is obtained

In straight triangular abc-a1b1c1
In the straight triangular prism abc-a1b1c1, ∠ ABC = 90 °, Aa1 = AC = BC = 2, D is a point on the edge of AB, e is the midpoint of edge BB1, and ∠ a1de = 90 °
1. Verification, CD vertical plane a1abb1
2. Dihedral angle c-a1e-d
Thank you~

Use vector? Have you learned it? Take B as the coordinate origin. BB1 AB BC as the XYZ axis, and then express the coordinates
1. Prove that the product of CD and two edges in the face is equal to 0
The second question is to find the normal vector of two surfaces and then set up a formula