Find the cube of X (x + 5) + 27 = 0

Find the cube of X (x + 5) + 27 = 0

Cube of (x + 5) + 27 = 0
（x+5）^3=-27
x+5=-3
x=-3-5
x=-8

Cube of 3x - square of 3x - 9x

Cube of 3x - square of 3x - 9x
=3x（x²-x-3）

Let x1, X2 Xn (n > 1) is independent and identically distributed, variance λ ^ 2 > 0, let y = (1 / N) ∑ (I = 1 ~ n) Xi, then ()
A.cov(X1,Y)=(λ^2)/n B.cov(X1,Y)=λ^2
C.D(X1,Y)=[(n+2)/n]*(λ^2) D.D(X1,Y)=[(n+1)/n]*(λ^2)

cov(X1,Y)=1/n·∑(i=1~n)cov(X1,Xi)=1/n·cov(X1,X1)=(λ^2)/n
So, choose a

To pave the floor of a room, 240 square bricks with a side length of 3 decimeters are needed. How many square bricks with a side length of 6 decimeters are needed?

If the side length of 6 decimeters square brick is selected, X pieces, (3 × 3) × 240 = (6 × 6) × x, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 3 × 3 × 2406 × 6, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 60; answer: if the side length of 6 decimeters square brick is selected, 60 pieces are required

High school cosine theorem
Let the three interior angles a, B and C of the triangle ABC form an arithmetic sequence, and the reciprocal of the three sides a, B and C also form an arithmetic sequence, and then calculate the angles a, B and C

A:
Angles a, B and C form an arithmetic sequence, so angle B is 60 degrees. Let angles a, B and C be
π/3-t,π/3,π/3+t,
From 2 / b = 1 / A + 1 / C,
From sine theorem
a/sinA=b/sinB=c/sinC,
SINB = √ 3 / 2 substituting,
4/√3=1/sin(π/3-t)+1/sin(π/3+t)
4/√3=[sin(π/3-t)+sin(π/3+t)]/[sin(π/3-t)sin(π/3+t)]
Expand to get
(4/√3)*[3/4(cost)^2-1/4(sint)^2]=√3cost
4{3/4(cost)^2-1/4[1-(cost)^2]}=3cost
4(cost)^2-3cost-1=0
(cost-1)(4cost+1)=0
The result shows that cost = 1
t=0,
This shows that angles a, B and C are all π / 3

Inverse function of y = x ^ SiNx
Y is the inverse function of SiNx power of X? Please write down the calculation steps
X for y, y for X, I know
I'm asking if the inverse function of this can be written as y =? The form of

This function has no inverse function
When x = k * PI (k is an integer), the independent variable and the dependent variable of two functions which are inverse to each other should correspond one by one
Y = x ^ SiNx = 1, that is to say, one y corresponds to more than one X

Stack 27 small cubes with edge length of 1cm into a large cube. How many square centimeters less is the surface area of this large cube than the sum of all the original small cubes?

The original 27 1 cm cube iron blocks are stacked into a large cube, and the volume sum is 27 cubic centimeters. Because 33 = 27, the edge length of the stacked large cube is 3cm, then: 1 × 1 × 6 × 27-3 × 3 × 6, = 162-54, = 108 (cubic centimeters). A: the surface product of the large cube is 108 square centimeters less than the sum of the original small cubes

The answer and solution of p9 question 4 in Grade 6
A cylindrical steel bar on a construction site has a cross section of 12.56 square centimeters and a length of 5.5 meters. It is known that each cubic decimeter of steel bar weighs 7.8 kg. How many kg does this steel bar weigh? (the number of kg is reserved)
Ask for a detailed solution, in short, let people understand on the line, direct listening to the answer is not interesting, it is better not to do

First, the volume of steel bar is calculated: v = sh = 0.1256 * 55 = 6.908 cubic decimeter;
Unit conversion: 12.56 cubic centimeter = 0.1256 cubic decimeter, 5.5m = 55 decimeter;
Weight of reinforcement = 6908 * 7.8 = 54 (rounded to the nearest whole number)

Making variable substitution x = LNT to simplify equation d ^ 2Y / DX ^ 2-dy / DX + e ^ 2x * y = 0

x=lnt
dx/dt=1/t
dy/dx=(dy/dt)/(dx/dt)=t dy/dt
d²y/dx²=[d/dt(dy/dx)]/(dx/dt)=t² d²y/dt²+t dy/dt
Substituting d ^ 2Y / DX ^ 2-dy / DX + e ^ 2x * y = 0
t² d²y/dt²+t dy/dt-t dy/dt+e^(2lnt)y=0
t² d²y/dt²+t²y=0
d²y/dt²+y=0
Hope to help you, hope to adopt, thank you~

The circumference of a rectangle is 24 cm, with three such rectangles can just spell out a square

That's three times the length and width
Width 24 ÷ 2 ÷ (3 + 1) = 3cm
Length 3x3 = 9cm