In the arithmetic sequence an, given A5 + A8 = a, what is the value of A2 + A5 + A8 + a11?

In the arithmetic sequence an, given A5 + A8 = a, what is the value of A2 + A5 + A8 + a11?

a2+a11=a5+a8=a
a2+a5+a8+a11=2a

Given that the sequence {an} is an arithmetic sequence, and A5 = 11, a8 = 5, then an=______ ．

In the arithmetic sequence {an}, from A5 = 11, a8 = 5, d = A8 − a58 − 5 = 5 − 113 = − 2. So an = A5 + (N-5) d = 11-2 (N-5) = - 2n + 21. So the answer is - 2n + 21

In the arithmetic sequence {an}, given A5 = - 1, a8 = 2, find A1 and D

According to the question: a8-a5 = 3D
So the solution is: D = 1
Because: A5 = a1 + 4D = - 1
The solution is: A1 = - 5

In the known arithmetic sequence {an}, A5 = - 1, a8 = 2, find A1, D and write its general formula

a1+4d=-1
a1+7d=2
a1=-5,d=1

How many kilos is one ton

1000 kg

A 1.47n iron ball is hung under the spring scale. Immerse the iron ball in water. The indication of the spring scale is 0.49n
1) Buoyancy of iron ball (2) volume of iron ball
(3) Is the iron ball hollow or solid? (the known density of iron is 7.9 × 103 kg / M)

1. The buoyancy of the iron ball is 1.47-0.49 = 0.98n2, the buoyancy of the iron ball is equal to the volume of the discharged water, that is, the volume of the submerged iron ball is ρ GV = 0.981000 * 9.8 * V = 0.98v = 10 ^ (- 4) m3, the volume of the solid iron ball of 1.47n is ρ GV = 1.47v = 1.47 / (7.9 × 10 ^ 3 * 9.8) = 1.9 * 10 ^ (- 5) m3

Find the functional relationship between the number of diagonal lines and the number of sides of a polygon,
Finding the functional relationship between the number of diagonal lines and the number of sides of a polygon
Notice the function relation!
The relation is d = n (n-3) / 2
What is the functional relation?

Or this
Generally, it is written as y = x (x-3) / 2 domain {x | x > 3, and X ∈ n}

As shown in the figure, two objects a and B with mass of M and 2m are stacked together and placed on a smooth horizontal ground. It is known that the maximum friction between a and B is μ times of the gravity of object A. if horizontal force is applied on a or B to make a and B keep relatively stationary and accelerate, what is the ratio of the maximum tension FA and FB applied on a and B?

When the force F acts on a, and a and B just don't slide relative to each other, for B, according to Newton's second law: μ mg = 2mA ① The same is true for the whole: FA = (M + 2m) a ② When the force F acts on B, and a and B just don't slide relative to each other, the second Newton's law for a is: μ mg = ma ′

Why is a negative number multiplied by a negative number equal to a positive number?
Is it a purely mathematical rule, or is there a factual example to prove it

How to understand the multiplication and division of negative numbers
Let - A and - B be two negative numbers
0=[a+(-a)]
So [a + (- a)] (- b) = 0
Distribution law by multiplication (it also applies to negative numbers)
[a+(-a)]（-b）=a*(-b)+(-a)*(-b)=0
a*(-b)=-ab
So (- a) * (- b) = 0 - (- AB) = ab
This is the reason why "negative is positive"

Two uniform disks with mass of M and 2M and radius of R and 2R are coaxially bonded together and can be wound through the disks

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