Arrange the remainder of 1,2,3,4 divided by 3 to get a group of numbers. What is the sum of the first 100 numbers in this group

Arrange the remainder of 1,2,3,4 divided by 3 to get a group of numbers. What is the sum of the first 100 numbers in this group

1 2 0 1 2 0 1 2 0.
The first 99 are 33 * 3 = 99
The 100th one
Total 100

Given the sum of the first n terms of the sequence {an} Sn = n & # 178; - 9N (1) find the minimum sum of the first n terms of an (2), and find the n value at this time

1.
When n = 1, A1 = S1 = 1 & # 178; - 9 × 1 = 1-9 = - 8
When n ≥ 2, an = SN-S (n-1) = n & # 178; - 9N - [(n-1) &# 178; - 9 (n-1)] = 2n-10
When n = 1, A1 = 2 × 1-10 = - 8, which also satisfies the general formula
The general formula of sequence {an} is an = 2n-10
two
Sn=(a1+an)n/2
=(-8+2n-10)n/2
=n²-9n
=(n- 9/2)² -81/4
When n = 4, n = 5, Sn has the minimum value (SN) min = 4 & # 178; - 9 × 4 = 16-36 = - 20
The minimum value of the sum of the first n terms is - 20, and the values of N are 4 and 5

If the reciprocal of 3-x equals 12, then X-1 = 1___ ．

According to the meaning of the question: 3-x = 2, the solution: x = 1, then X-1 = 1-1 = 0

How does a & sup2; + 2B & sup2; + C & sup2; - 2ab-2ac decompose a factor

=-2b(a-b)+(a-c)^2
Specific steps = (a-b) ^ 2 + (A-C) ^ 2 + B ^ 2-A ^ 2, then use the square difference
Can you ask if this is a high school question or a junior high school question

There are four numbers, three of which are added each time, and their sums are 15, 17, 19 and 21 respectively. Why are these four numbers 3, 5, 7 and 9 respectively?

15. 17, 19 and 21, respectively,
Suppose that the four numbers are in descending order: A, B, C and D
Then a + B + C = 15, a + B + D = 17, a + C + D = 19, B + C + D = 21
Obviously, d-c = 2, C-B = 2, B-A = 2
That is, the four numbers are four adjacent even or odd numbers
And three even numbers add up to even numbers
So these are four adjacent odd numbers
The three smallest numbers add up to 15
Then the middle of the three numbers is 5
So the other two are three and seven
And the last one is obviously 9

What is the basis of the addition and subtraction method of binary linear equations?

It is to subtract or add the same elements = 0 to eliminate one of them
x+y=12
x-y=1
Then the first formula plus the second formula is 2x = 13
The principle of subtraction is the same as above

97*2000-96*2001=

97*2000-96*2001
= 97*2000-96*(2000+1)
= 97*2000-96*2000-96
=2000*(97-96)-96
=2000-96
=1904

Let n denote any integer. Please use an algebraic expression containing n to express: what is the number of the remaining 2 divided by 3

3n+2

How to divide 7200 by 25

100/25=4 4*72=288

The base of a triangle is 5cm long. If the base is extended by 2cm, the area of the triangle will be increased by 5cm. What is the area of the original triangle

The height is 5 × 2 △ 2 = 5 cm
So the original area is 5 × 5 △ 2 = 12.5 square centimeters