Known x + x ^ 2 + x ^ 3 + +x ^n=a0+a1(x-3)+a2(x-3)^2+…… +An (x-3) ^ n (n belongs to n *). And an = A0 + A1 + A2 + +an Then Liman / 4 ^ n= I can't understand the process on the Internet. Why should I make x = 4?

Known x + x ^ 2 + x ^ 3 + +x ^n=a0+a1(x-3)+a2(x-3)^2+…… +An (x-3) ^ n (n belongs to n *). And an = A0 + A1 + A2 + +an Then Liman / 4 ^ n= I can't understand the process on the Internet. Why should I make x = 4?

x+x^2+x^3+…… +x ^n=a0+a1(x-3)+a2(x-3)^2+…… +an(x-3)^n
Let x = 4, then the right side of the equation becomes A0 + A1 + A2 + +An is the required an (this is called assignment method)
Then an = 4 + 4 ^ 2 + 4 ^ 3 +. + 4 ^ n

How to solve 4x = 7x-5?

Transference
7x-4x=5
3x=5
x=5÷3
x=5/3

A barrel of oil weighs 120 kg. After half use, it still weighs 65 kg. How many kg does the barrel weigh?

Half oil mass: 120-65 = 55 kg
Mass of oil barrel: 120-55 × 2 = 10kg

The continuity and differentiability of functions are discussed
The continuity and differentiability of function f (x) = {(1-cos2x) / x, X ≠ 0 at x = 0 are discussed
x, x=0

When x tends to zero, limf (x) = (1-cos2x) / x = 2 * (SiNx) ^ 2 / x = 0. When x = 0, f (x) = 0. Limf (x) = f (0) = 0, so the function is continuous at x = 0. F '(0) = limf (x) / x = (1-cos2x) / x ^ 2 = 2 * (SiNx) ^ 2 / x ^ 2 = 2

Who knows the operation and expression of C language
Multiple choice questions (in the alternative a, B, C and D of each Subquestion below, two or more options are correct. Please choose the correct option. No score will be given for multiple choice, less choice or wrong choice.)
1. Set the description int a = 0, B = 1, C = 2; the value of the following expression is 1 (for logical expression representing non-0), there is ()
\x05A.a && b \x05\x05B.++a C.a && b>c \x05 D.c||a
2. Let a, B, C be int type variables, and a = 3, B = 4, C = 5, the following expression value of 0 is ()
\x05A.'a' && 'b'\x05\x05B．a>b\x05\x05C．a || b+c && b-c\x05\x05 D．!(a

1、BD 2、BD3、ACD 4、ABD 5、BD 6、AD 7、AC 8、BC 9、AD 10、ACD

What is the sentence about the rapidity of water in the Three Gorges

As for the summer water Xiangling, along the trace block

The infinitesimal part of 1-cosx ~ 1 / 2 (2 ^ x)~

Equivalent infinitesimal

There are 20 girls in class 61. The ratio of girls to boys is 4:5. How many students are there in the class

Number of boys x
20：x=4:5
There are 25 boys and 45 students in the class

75 × 98 = how to calculate this problem in a simple way? Thank you

Equal to 75X (100-2) equal to 75x100-75x2 equal to 7500-150 equal to 7350

Given the general term formula of the equal ratio sequence an, an = 3 * (0.5) ^ (n-1) and BN = a3n-2 + a3n-1 + a3n, prove that BN is equal ratio sequence

The {an} is an equal ratio sequence,
Then an + 1 = an * q, n > = 1
bn+1/bn=(a3n+1+a3n+2+a3n+3)/(a3n-2+a3n-1+a3n)
=(q^3*a3n-2+q^3*a3n-1+q^3*a3n)/(a3n-2+a3n-1+a3n)
=q^3
The above formula holds for any positive integer n
Then {BN} is an equal ratio sequence