What are the definitions of constants and variables

What are the definitions of constants and variables

Constant refers to relatively fixed data
Variables are data that change randomly
For example, if you calculate the area of a circle, the radius is a variable, and PI (PI 3.14159) is a constant

Explain the meaning of the words in brackets
Most (like) children die, stream head lie peel lotus

Like, like
Meaning: naughty and lovely little son, lying on the head of the stream, peeling lotus, the simple and honest naive state makes people especially like

If 2a-b = 5, what is the value of polynomial 6a-3b?

15
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What is the condition for the existence of limf (x) defined by function f (x) at x = x0

Sufficient and unnecessary conditions

If a ^ 2 + A-1 = 0, find the value of a ^ 2004-A ^ 2005-a ^ 2006
A ^ 2004 is the 2004 power of A
A ^ 2005 is the power of A
A ^ 2006 is the power of A
Note: the method of quoting common factor is used

a^2004-a^2005-a^2006
=a^2004*(1-a-a^2)
=-a^2004(a^2+a-1)
=-a^2004*0
=0

If the square of x = 2x, then x can only be 2

Wrong
X²=2X
x²-2x=0
x（x-2)=0
So X1 = 0, X2 = 2

6 out of 35 = 26 out of 45 △ 13 out of 25

6 out of 35 = 26 out of 45 △ 13 out of 25
X-35:6 = 45:26 × 13:25
6 out of 35 = 10 out of 9
X = 10 / 9 + 6 / 35
X = 404 / 315

Let vector group A1, A2, A3 be linearly independent. It is proved that vector group a1-a2-2a3, A2-A3, A3 are also linearly independent

Let x (a1-a2-2a3) + y (A2-A3) + ZA3 = 0, then
xa1+(-x+y)a2+(-2x-y+z)a3=0,
The vectors A1, A2, A3 are linearly independent,
∴x=0,-x+y=0,-2x-y+z=0,
The solution is x = y = z = 0,
The vector groups a1-a2-2a3, A2-A3, A3 are also linearly independent

Solving equation (10 + 2x) (76-4x) = 1080

760-40x＋152x－8x²＝1080
8x²－112x＋320＝0
x²－14x＋40＝0
（x－10）（x－4）＝0
∴x1＝4 2＝10

Arrange a group of rational numbers x1, X2, X3, x4, X5 from small to large, each of which is less than - 1, please use“

Using the number axis analysis, we can get the following results
x1＜x3＜x5＜1＜-x4＜-x2