When n is a positive integer, the value of N & sup3; - N must be a multiple of 6

When n is a positive integer, the value of N & sup3; - N must be a multiple of 6

(n*n*n-n)=n(n*n-1)=n(n+1)*(n-1)
The above formula is equal to (n-1) * n * (n + 1)
It is equal to the product of three consecutive positive integers
Three consecutive positive integers contain at least one multiple of 3 and one even number
That is: (n-1) * n * (n + 1) can be divided by 3 and then by 2, that is, by 6, so the value of (n * n * N-N) is a multiple of 6

It is proved that when n is a positive integer, the value of n * n * N-N must be a multiple of 6

N*N*N-N=N*(N*N-1)=(N-1)*N*(N+1)
That is, it is equal to the multiplication of three adjacent numbers. We can see that there is at least one even number and a multiple of three, so it must be a multiple of 6

Some three digits are equal to the cubic sum of its digits. Design an algorithm to find such three digits
As long as the algorithm, not the program

A number "ABC"
ABC=100*A+10*B+C = A*A*A+B*B*B+C*C*C
Loop from 100 to 999, and judge if true, output "ABC"

The rational numbers corresponding to points a, B, C and D on the number axis are all integers. If point a corresponds to rational number a, point B corresponds to rational number B, and b-2a = 7, then the origin on the number axis should be ()
A. A point B. B point C. C point D. D point

∵ point B corresponds to rational number B, ∵ a = B-4, ∵ b-2a = 7, ∵ B-2 (B-4) = 7, ∵ B = 1, a = - 3. From the graph, if point C is between point a and point B, then point C is the origin, so select C

Given the parabola y = ax & # 178; + BX + C, if 4a-2b + C + 4 = 0, then the point that the parabola must pass through is a (2,4) B (- 2,4) C (- 2, - 4) d (2, - 4)

Choose C
We know the parabola y = ax & # 178; + BX + C, so we have
When x = - 2
y=4a-2b+c
If 4a-2b + C + 4 = 0, then
When x = - 2
y=-4
The point a parabola must pass is C (- 2, - 4)

There is an AC contactor. The coil voltage is 380V and the wire diameter is 0.09mm. Now it is used in the power supply of 220V. How to refit it?
Find out the number of coil turns and the diameter of the wire after replacement

Generally, there are direct products for sale. If you transform yourself, you will not lose. If you need 0.12 diameter enameled wire, you need to calculate the number of turns according to the ratio of 220 / 380

Y + 2x is equal to 1, find the value of (y + 1) square minus (y square minus 4x)

Gu Zhun AA|
First, simplify
(y+1)²-(y²-4x)
=y²+2y+1-y²+4x
=2y+4x+1
∵y+2x=1
Ψ 2Y + 4x = 2 (multiply both sides by 2)
The original formula = 2 + 1 = 3

How to design experiments to prove that the change of filament temperature will lead to the change of resistance value

Measuring resistance by voltammetry

Ask some math questions about fractions,
(1)
[(5xy)/(x²+xy)]*[(xy+y²)/(2x²y²)]^3
(2)
[(x^3-3x+4)/(x²+2x-3)]÷[(x²-16)/(x²+6x+9)]
(3)
(x²+x-3)/(x²+x-2)+1=(2x²+4x+1)/(x²+2x+1)
(4)
Given that a & sup2; + 4A + 1 = 0 and (a ^ 4 + Ma & sup2; + 1) / (2a ^ 3 + Ma & sup2; + 2a) = 3, try to determine the value of M
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Well, well written, I'll add points and say,

1 (5xy)/(x²+xy)=5y/(x+y) (xy+y²)/(2x²y²)^3=(x+y)/(2x²y)^3 [5y/(x+y)]*[(x+y)/(2x²y)]^3=[5/(x+y)]*[(x+y)^3/(2x^6y²)]=5*(x+y)^2/(8x^6y²)2 x^3...

How much is 2.5 square meters of hard copper wire per 100 meters? 4 square meters? 6 square meters?

2.5 copper wire 100 meters, resistance 0.72 Ω, 15A current voltage drop of about 10V, but, need two lines to work, that is, 15A current, the electrical voltage is 220-20 = 200V (can work). 4mm2 copper wire 20A current step-down 18V (can work). 6m2 copper wire 30A current step-down 18V (can also be normal