If sample x1, X2 The sample 3x1 + 5, 3x2 + 5 The average and variance of 3XN + 5 are () A. .x、s2B. 3.x+5、s2C. 3.x+5、9s2D. 3.x+5、（3s+5）2

If sample x1, X2 The sample 3x1 + 5, 3x2 + 5 The average and variance of 3XN + 5 are () A. .x、s2B. 3.x+5、s2C. 3.x+5、9s2D. 3.x+5、（3s+5）2

∵x1，x2，… The average of, xn & nbsp; is. X, ｜ X1 + x2 + +xn=n.x，∴3x1+5，3x2+5，… The average of 3XN + 5 is: 3x1 + 5 + 3x2 + 5 +3xn+5）÷n=[3（x1+x2+… +xn）+5n]÷n=（3n.x+5n）÷n=3.x+5．∵x1，x2，… The variance of, xn & nbsp; is S2, ｜ 1n [(x1-x) 2 + (x2-x) 2 + +（xn-x）2]=s2，∴3x1+5，3x2+5，… The variance of 3XN + 5 is: 1n [(3x1 + 5-3. X-5) 2 + (3x2 + 5-3. X-5) 2 + +（3xn+5-3.x-5）2]=1n[（3x1-3.x）2+（3x2-3.x）2+… +（3xn-3.x）2]，=1n[9（x1-.x）2+9（x2-.x）2+… +9（xn-.x）2]，=9n[（x1-.x）2+（x2-.x）2+… +(xn -. X) 2], = 9s2

If data x1, X2, X3 X = 5, variance σ 2 = 2, then data 3x1 + 1, 3x2 + 1, 3x3 + 1 The variance of 3XN + 1 is______ ．

∵x1，x2，x3，… The variance of, xn is 2,... 3x1 + 1, 3x2 + 1, 3x3 + 1 The variance of 3XN + 1 is 32 × 2 = 18

Known x1, X2 If the variance of XN is 2, then 3x1 + 5, 3x2 + 5 The standard deviation of 3XN + 5 is______ ．

Let x1, X2 The average of XN is. X, that is. X = 1n (x1 + x2 +...) +Xn) then samples 3x1 + 5, 3x2 + 5 The average of 3XN + 5 is = 1n (3x1 + 5 + 3x2 + 5 +...) +3xn+5 ）=1n×3（x1+x2+… +Xn) + 5 = 3. X + 5; from the formula of variance S2 = 1n [(x1 -. X) 2 + (X2 -. X) 2 + ...

You don't have to explain what you mean to others. People will understand what idiom you are

It goes without saying~~~~~~~~~~~~~~~~~~~

What are the idioms to describe honesty?

Be honest and honest

What idioms are used to describe many people or things?
More than 30

There are numerous, numerous, and numerous people: a sea of people, a crowd of people, a large number of people, a bustling city, a lot of traffic, people coming and going, one after another, Xiang Bei Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Xiang Material: colorful, dazzling, various, rich and colorful, not stick to one pattern, various patterns

Idioms for many people

[shoulder to shoulder] shoulder to shoulder, back to back. Describe crowded people. [three to top four] describe many people, continuous connection. Same as "three to top five". "[three to top five] describe many people, continuous connection

A reservoir is designed in a factory. As shown in the figure, the liquid level height of tank a of water source is H1 = 3M and remains unchanged. There is a small water outlet at the bottom of the tank, with an area of S1, S1 = 0.1m2. Under the hole, a piston with a cross-sectional area of S2 is connected with lever BC, S2 = 0.24m2. The lever can rotate up and down around the B end, and there is a hollow cylindrical float at the other end, with a cross-sectional area of S3, S3 = 0.8m2. Bo is the total lever In the original design, when the lever is horizontal, the depth of immersion of the float is H2, h2 = 0.7m, and the piston can just bet on the water outlet. However, when it is used, it is found that when the piston is still a short distance from the water outlet, the float will not float up. At this time, the depth of immersion of the float is H3, H3 = 1m. In order to make the piston block the water outlet automatically, we have to subtract part of the mass of the float, and set the subtracted mass as M (when G is 10N / kg and lever level, Bo is still considered as lever length 13, the mass of piston, connecting rod and lever is ignored, the buoyancy of lever is ignored, and the liquid level change of reservoir caused by the volume change of float immersed in water is ignored.) try to find out (1) how high the piston should rise; (2) how much the float should subtract mass m '

Let the original gravity of the float be g and the length of the lever be L. after the weight of the float is reduced, the weight is g ', which changes from inclined to horizontal. As shown in the figure, the rising height of the lever C end is EC = h3-h2 = 0.3m, and the rising height of the piston △ h is the length of OD; According to the mathematical knowledge, triangle BDO is similar to triangle BEC, so: doec = Bobc = bdbe, because Bo is the total length of lever 13, so: doec = Bobc = bdbe = 13, because EC = 0.3m, so od = 0.1M, that is, the length of piston rising height do segment is △ H = 0.1M; (2) Before the piston weight reduction, when the lever is balanced, the fulcrum is B. taking the float as the research object, the resultant force on the C end is f-floating-g = (s3h3 ρ water G-G), the arm of the force is be, the force on the o point is f-pressure = ρ water GS2 (H1 + △ h), and the arm of the force is set as BD. according to the lever balance conditions, we can get: (f-floating-g) be = f-pressure BD, that is: (s3h3 ρ water G-G) be = ρ water GS2 (H1 + △ h) BD, bdbe = 13, That is: 3 (s3h3 ρ water G-G) = ρ water GS2 (H1 + △ h), substituting into the data: 3 (0.8m2 × 1m × 103kg / m3 × 10N / kg-g) = 103kg / m3 × 10N / kg × 0.24m2 (3m + 0.1M), the solution is: g = 5520n. After the float weight is reduced, when the lever is balanced, the force analysis is carried out with the lever as the research object: the resultant force on the C end is f'floating-g '= s3h2 ρ water G-G', the force arm is BC, and the force on the o point is f'pressure =According to the lever balance: (s3h2 ρ water G-G ′) BC = ρ water gs1h1 & nbsp; Bo, that is: 3 [s3h2 ρ water G-G ′] = ρ water gs1h1, substituting into the data: 3 (0.8m2 × 0.7m × 103kg / m3 × 10N / kg-g ′) = 103kg / m3 × 10N / kg × 0.1m2 × 3M. The solution is: G ′ = 4600n. The gravity of the subtracted float: △ g = G-G ′ = 5520n-46oon = 920n, the mass of the subtracted float: △ M = △ GG = 920n10n / kg = 92kg The quantity M 'is 92 kg

There is a column of numbers: 1 / 1, 1 / 2, 2 / 2, 1 / 3, 2 / 3, 3 / 3. What is the sum of the third number?

=1/1+1/2+2/2+1/3+2/3+3/3+...+1/63+2/63+...43/63 =1+1.5+2+2.5+3+...+31.5+1/63+2/63+...43/63 =1007.5+1/63+2/63+...43/63 =1007.5+946/63 =1022.515873015873

There is a string of numbers: 11, 12, 22, 13, 23, 33, 14 What is the sum of its first 1996 numbers?

There is one number with 1 as denominator, sum S1 = 1, two numbers with 2 as denominator, sum S2 = 12 + 22 = 32, three numbers with 3 as denominator, sum S3 = 13 + 23 + 33 = 2 There are n numbers with n as the denominator, sum Sn = 1n + 2n + NN = n (n + 1) 2n = n + 12