If the average of samples X1 and x2.xn is 9 and the variance is 2, what is the average and variance of the other samples X1 + 2 and X2 + 2.xn + 2?

If the average of samples X1 and x2.xn is 9 and the variance is 2, what is the average and variance of the other samples X1 + 2 and X2 + 2.xn + 2?

(x1+x2+…… +xn）/n=9
(x1+2+x2+2+…… +xn+2）/n
=[(x1+x2+…… +xn）+2n]/2
=(9n+2n)/n
=11
Let the maximum number be Xa and the minimum number be XB
Then the maximum number of the other sample is Xa and the minimum is XB
(xa+2)-(xb+2)=xa+2-xb-2
=xa-xb
=2

Calculation - 8x ^ 2Y · (a-b) · 1 / 2XY ^ 2 · (1 / 2b-1 / 2a) ^ 2

-8x^2y·(a-b)·1/2xy^2·(1/2b-1/2a)^2
=-4x^3y^3*(a-b)*1/4(a-b)^2
=-x³y³（a-b）³
If you don't understand this question, you can ask,

Taking both sides AB and AC of triangle ABC as sides, square ACDE is made outwards. Square abgf and m are the midpoint of BC. It is proved that am is vertical
Am vertical ef

Method 1: MP / / AC is made through M, AB is crossed with P, Ma is extended, Fe is crossed with Q, then: MP / AE = AP / AF = 1 / 2; angle FAE + angle BAC = 180 and angle BAC + angle APM = 180, so angle FAE = angle APM; so triangle APM is similar to triangle FAE, so angle PAM = angle AFE, and angle PAM + angle FAQ = 90, so angle AFE + angle FAQ = 90, so

If the cube of (a + 1) x + the power B of X - 3x + 5 is a quadratic trinomial of X, find the power 2012 of (a + b)

Because it is a quadratic trinomial of X, the highest power of X is 2, so there is no cube of X, so a + 1 = 0
So a = - 1;
The reason is the same as above. In the other three terms, the only place where x can be quadratic is the power B of X, so B = 2
Then a + B = - 1 + 2 = 1
Original formula = (a + b) ^ 2012 = 1 ^ 2012 = 1

The rational numbers corresponding to four points a, B, C and D on the number axis are integers a, B, C and D respectively, and C-2A = 8. Where is the origin
The number axis is a, B, C and D in order. A and B are separated by two units, B and C are separated by two units, and C and D are separated by two units

1) Let a be x, then B, C and D are x + 2, x + 4 and X + 6 respectively
C-2A = 8 x + 4-2x = 8 x = - 4 C = 0, the origin is C;
2) Let a be x, then B, C and D are X-2, x-4 and X-6 respectively
C-2A = 8 x-4-2x = 8 x = - 12 the origin is 12 units to the right of A

It is known that the quadratic power of ax - x = 4 is a linear equation of one variable with respect to x, then a = ()

A = - 1, for example - 4x = 6, a = - 4, just look at the number in front of X. I'm on the third day of this year. If you don't understand anything, please ask me

How to connect 380V voltage to 220 V contactor coil?

Connect three identical contactors into star type, and then connect to three-phase 380V, but ensure that the three contactors are powered on at the same time, otherwise it is useless

(x square plus y square minus 1) square minus 4x square y square

(x²+y²-1)²-4x²y²=(x²+y²-1)²-(2xy)²=(x²+y²-1+2xy)(x²+y²-1-2xy)=[(x+y)²-1][(x-y)²-1]=(x+y+1)(x+y-1)(x-y+1)(x-y-1)

Relationship between resistance and temperature
Tell me how he became
For example, when the temperature is greater than XX, XXX ohm
Less than XX, XXX ohm
20: Critical point
The reason also says, (must) detailed a bit best
Is the higher the temperature, the greater the resistance?

It has something to do with materials. There is no fixed point
Metal conduction is electron conduction. Electrons drift directionally under the action of electric field to form current in metal. When electrons move directionally in metal conductor, the smaller the obstruction, the smaller the resistance of conductor. On the contrary, the greater the obstruction, the less free they move and the greater the resistance of conductor
In the metal conductor, although the atomic realms in the crystal lattice basically keep regular arrangement, they are not static. Each atomic realms keep thermal vibration near its regular position, The thermal vibration of atoms in the whole conductor does not have a unified pace. In this way, the regularity of the arrangement of atoms is destroyed to a certain extent, and the obstruction to the movement of electrons is formed. The farther the thermal vibration of atoms is away from its regular position, the more chances of collision with electrons, the greater the obstruction to the drift of electrons, and the greater the resistance of the conductor
To sum up, the answer to the question is not hard to come out, because when the temperature rises, the thermal vibration of the atomic real increases, and the amplitude of the vibration increases. As a result, the chances of colliding with the atomic real and the times of colliding increase, so the resistance of the metal conductor increases, The relationship between resistance and temperature is
R ＝ R 0 ＋（ 1 ＋α t ）
Where R 0 is the resistance of the metal conductor at 0 ℃ and α is the temperature coefficient of resistance of the metal conductor. The temperature coefficient of resistance α of different metal materials is also different
But the resistance of some alloys changes little with temperature

Mathematical problems about fractions
1. Given X / 3 = Y / 5 = Z / 4, find the values of (x + y + Z) / Y and (x + y + Z) / (Y-Z)
2. Party A and Party B set out from both places of AB at the same time and walk in opposite directions. After meeting at C, Party A arrives at B after T1 hours, and Party B arrives at a after T2 hours. Suppose AC = S1, BC = S2, then what is T1 / T2?

1. The way to solve a problem like this is to set K. if it's a multiple-choice question, it can replace the special value, such as x = 3, y = 5, z = 4. Here is a short answer question, you can't use the special value method. The specific solution is as follows: let X / 3 = Y / 5 = Z / 4 = k, so x = 3k, y = 5K, z = 4K, so (x + y + Z) / y = (3K + 5K + 4K) / 5K = 12 /