How does Mathematica calculate numbers? A set data, I want to know the number that satisfies the condition x belongs to (- 1,1)!

How does Mathematica calculate numbers? A set data, I want to know the number that satisfies the condition x belongs to (- 1,1)!

There are many ways, such as:
List = randomreal [{- 5,5}, 20] (* here, for example, randomly generate an array *)
Length@Select [list,-1 < # < 1 &]

Using Mathematica software to calculate the derivative of implicit function
Finding y = x + iny is like that function also has the derivative dy / DX of y = y (x)

y = (x + Log[y]) ,
Let z = y - (x + log [y]) = 0,
Dt[y - (x + Log[y]),x] ,
-1 + Dt[y,x] - Dt[y,x]/y

Using Mathematica to calculate the distance from point to line
Find the distance from the point (1,1,4) to the line L: (x-3) / - 1 = Y / 0 = (Z + 1) / 2,

f[t_ ] := (-t + 3 - 1)^2 + 1 + (2 t - 1 - 1)^2
Sqrt[f[t]/.Solve[f'[t]==0,t][[1]]

A cone and a cylinder have the same base and height. It is known that the volume of the cone is 24 cubic decimeters less than that of the cylinder. What is the volume of the cylinder and the cone?

A cone and a cylinder have the same height and the same base. The volume of a cone is 1 / 3 of that of a cylinder
The volume of cone is 24 / 2 = 12 cubic decimeter
The volume of the cylinder is 12x3 = 36 cubic decimeters

Let a, B, C, D, e, F, G, h, I and K represent ten different natural numbers greater than 0
Let's know that a, B, C, D, e, F, G, h, I, K represent ten different natural numbers greater than 0. Let's make the following equation: B + C = a, D + e = B, e + F = C, G + H = D, H + I = e, I + k = f hold. What is the minimum of a?

20
A = G + 3H + 3I + K, to minimize a, take H = 1, I = 2, then E = 3; if G = 4, then d = 5, B = 8; k = 7, f = 9, C = 12, then a = 20
If k = 4, then f = 6, C = 9, g = 7, d = 8, B = 11, a = 20

Solving inequality (Group) (1) 2x + 1 / 3-6x-7 / 4 ≤ 2x + 5 / 12-1
（2）{3+x

(2) 3+x-1
3x-3-6

"Chicken" in the sentence refers to (), "mother chicken" refers to (), the advantage of this writing is ()

"Chicken" refers to students, and "mother chicken" refers to teacher Yin Xuemei. The advantages of this writing are: using metaphors to vividly depict the characters, highlighting that teachers care for their students like their mothers

The square of (x-3) and | x + Y-1 | are opposite numbers to each other. Find the value of XY

∵ opposite numbers
∴x-3=0
x=3
x+y-1=0
y=-2
xy=3*-2
=-6

In an integer subtraction formula, the sum of the subtracted, the subtracted and the difference is 28, and the difference is two fifths of the subtracted, then the subtraction is ()

Let the subtracted be a, the subtracted be B, and the difference be c. then there are a + B + C = 28, C = 2 / 5b, and the most important thing is A-B = C. A = 7 / 5b is transformed into 7 / 5B + B + 2 / 5B = 28. Finally, the solution is a = 14, B = 10, C = 4

If the absolute value of X-1 + (XY-2) &# 178; = 0
1/xy+1/（x+1)（y+1)+1/（x+2)（y+2)+…… +1/（x+2012)（y+2012)
Find the value of that formula

From X - 1 | + (XY - 2) & # 178; = 0, we can know that X - 1 = 0, XY - 2 = 0. By solving these two equations, we can get x = 1, y = 2, so: 1 / XY + 1 / (x + 1) (y + 1) + 1 / (x + 2) (y + 2) + +1/（x+2012)（y+2012)＝1/（1×2）+ 1/(2×3) + 1/(3×4)+…… + 1/(2013×2...