If the first n terms of sequence {an} and Sn = n * 2-4n + 1 are known, then | A1 | + | A2 | + +|The value of A1 | 0 is

If the first n terms of sequence {an} and Sn = n * 2-4n + 1 are known, then | A1 | + | A2 | + +|The value of A1 | 0 is

a1=-2,
From A2, an = SN-S (n-1) = (n ^ 2-4n + 1) - [(n-1) ^ 2-4 * (n-1) + 1] = 2n-5,
So A2 = - 1, A3 = 1, when n ≥ 2, an = 2n-5 > 0
So | A3 | + | A4 | + +|a10|=S10-a1-a2=164
So | A1 | + | A2 | + +|a10|=164+|a1|+|a2|=164+2+1=167
Please help me to convert the physical units
0.015km=1.5X____ m=1.5X_____ dm=1.5X______ cm=1.5X______ Mm
12.5mm=1.25X_____ m=1.25X_____ Km
10nm=10X_____ cm=1.0X_____ M
Note: X is a multiplication sign
10 10^2 10^3 10^4
10^-2 10^-4
10^-6 10^-8
Let's talk about it,!
++++++++++
What does the ^ of 10 ^ 2 mean?
Cut a circle, divide it into 16 parts, and form a triangle or trapezoid. The area of the circle is approximately () of the area of the triangle?
Cut it into a circle or a trapezoid, and put it into a triangle.
①S△=A×H÷2
② A is equal to () / () of the circumference of the circle, and H is equal to () times of the radius of the circle.
So s △ = () / () C × () r △ 2
=（ ）/（ ）×2πR×（ ）R÷2
=（ ）
（2）
① S trapezoid=________________ (formula)
② A is equivalent to () / () C
B is equivalent to () / () C
H is equivalent to () r
So s trapezoid = {() / () C + () / () C} × () r △ 2
=（ ）/（ ）C×（ ）r÷2
=（ ）/（ ）×2πR×（ ）R÷2
=（ ）
Cut out a circle and divide it into 16 parts to form an approximate triangle or trapezoid. ① s △ = a × h △ 2. ② A is equivalent to (1) / (4) of the circumference of the circle, and H is equivalent to (4) times of the radius of the circle. So s △ = (1) / (4) C × (4) r △ 2 = (1) / (4) × 2 π R × (4) r △ 2 =
One
The sequence {an} satisfies an + 1 + an = 4n-3 (n ∈ n *) (I) if {an} is an arithmetic sequence, find its general term formula; (II) if {an} satisfies A1 = 2, Sn is the sum of the first n terms of {an}, find s2n + 1
(1) According to the meaning of the title, an + 1 + an = 4n-3 ①an+2+an+1=4n+1… ②．… (2 points) ② - ① get an + 2-An = 4, ∵ {an} is an arithmetic sequence, let the tolerance be D, ∵ d = 2, (4 points) ∵ a1 + A2 = 1 ∵ a1 + A1 + D = 1, ∵ A1 = − 12. (6 points) ∵ an = 2n − 52. (7 points) (Ⅱ) ∵ A1 = 2, a1 + A2 = 1, ∵ A2 = - 1. (8 points) and ∵ an + 2-An = 4, ∵ the odd and even terms of the sequence form an arithmetic sequence, the tolerances are 4, ∵ a2n-1 = 4n-2, A2N = 4n-5. (11 points) ）S2n+1=（a1+a3+… +a2n+1）+（a2+a4+… +A2N) (12 points) = (n + 1) × 2 + (n + 1) N2 × 4 + n × (− 1) + n (n − 1) 2 × 4 = 4n2 + N + 2. (14 points)
Who knows the conversion rate between units? Thank you
Length, weight, area, time, currency. No feet, inches or anything. For example: 1 kilometer = 1000 meters, 1 meter = 10 decimeters, adjacent or not adjacent
Square kilometer = 100 hectare 1 hectare = 10000 square meter 1 square meter = 100 square decimeter 1 square decimeter = 100 square centimeter 1 square centimeter = 100 square millimeter 1 kilometer = 1000 meter 1 meter = 10 decimeter 1 decimeter = 10 centimeter 1 centimeter = 10 millimeter 1 kilogram = 1000 gram 1 ton = 1000 kilogram 1 square meter = 100 square decimeter 1 square decimeter = 100 square centimeter 1 square centimeter = 1 square millimeter 1 year = 365 days 1 day = 24 hours 1 hour = 60 minutes 1 minute = 60 seconds 1 liter = 1000 ml = 1000 CC
When deducing the area formula of a circle, the circle is divided into several equal parts to form an approximate rectangle
It is known that the length of a rectangle is 9.42 cm more than the width, and the area of a circle is ()
Let the width of rectangle be x, so the length is 9.42 + X, the area of circle s = (9.42 + x) x = 9.42x + X & sup2; = 3 × 3.14x + X & sup2; = 3 π x + X & sup2;, the area of circle s = π R & sup2;, R is the radius of circle, so π R & sup2; = 3 π x + X & sup2;, let X & sup2; = R & sup2; then, 3 π x
Let the sum of the first n terms of the sequence {an} be Sn, A1 = 2, and A1, Sn + 1, 4sn form an arithmetic sequence, (1) find the general formula of {an}
(2) , find Sn, and find Lim Sn / (T ^ n), where t is a normal number
In Sn + 1 is n + 1, not Sn plus 1
(1) It is known that A1 = 2, and A1, s (n + 1), 4sn are equal difference sequence, so 2S (n + 1) = 2 + 4sn, so s (n + 1) = 2Sn + 1, so s (n + 1) + 1 = 2Sn + 2 = 2 (Sn + 1) so {Sn + 1} is equal ratio sequence with S1 + 1 = a1 + 1 = 2 + 1 = 3, so Sn + 1 = 3 * 2 ^ (n-1) so Sn = 3 * 2 ^ (n-1) - 1. When n ≥ 2, an = Sn -
Grade 5 Volume 2 Mathematical unit conversion rate all, O (∩)_ Thank you
Length unit:
1 km = 1000 m 1 m = 10 decimeter = 100 cm 1 decimeter = 10 cm 1 cm = 10 mm 1 cm = 10 mm
area unit:
1 square kilometer = 1000000 square meter = 100 hectare 1 hectare = 10000 square meter 1 square meter = 100 square decimeter = 10000 square centimeter 1 square decimeter = 100 square centimeter
Volume unit:
1 cubic meter = 1000 cubic decimeter = 1000000 cubic centimeter 1 cubic decimeter = 1000 cubic centimeter
1 liter = 1000 ml 1 liter = 1 cubic decimeter 1 ml = 1 cubic centimeter
Quality unit:
G = 1 000 kg
Time unit:
1 year = December = 365 days (ordinary year) or 366 days (leap year) 1 month = 28 days (February of ordinary year), 29 days (February of leap year), 30 days (April, June, September and November), 31 days (January, March, may, July, August, October and December) 1 day = 24:1 hour = 60 minutes = 3600 seconds
1 minute = 60 seconds
It's 10 in length and 60 in time
Between areas is 100, between volumes is 1000
Between volumes is 1000
Between the masses is 1000
That should be all for fifth grade
1 cubic centimeter = 1000 mm and 179; 1 cubic decimeter = 1000 cm and 179;
1 cubic meter = 1000 decimeters and 179; 1 liter = 1000 ml
1 liter = 1000 cm and 179;... Unfold
1 cubic centimeter = 1000 mm and 179; 1 cubic decimeter = 1000 cm and 179;
1 cubic meter = 1000 decimeters and 179; 1 liter = 1000 ml
1 liter = 1000 cm and 179; 1 liter = 1 decimeter and 179;
1 ml = 1 cm cubic 5 cm
In the triangle ABC, a = π / 3, the area is root 3, find the minimum perimeter of the triangle ABC, and explain the shape of the triangle when the perimeter is minimum
Tell me what you know,
=a+b+c
Area s = 1 / 2bcsin π / 3 = √ 3, BC = 4, B + C > = 2 √ (BC) = 4 (take equal sign when B = C = 2)
Cosine theorem a & # 178; = (B + C) &# 178; - 12 > = 4 & # 178; - 12 = 4 a > = 2
So when a = b = C = 2, the minimum perimeter of ABC is 6, and the triangle is equilateral
Equilateral triangle
A / Sina = B / SINB = C / sinc = 2R (R is the diameter of ABC circumcircle of triangle)
The area of triangle ABC = 1 / 2 · BC · Sina = √ 3 / 4 · BC = √ 3, ｜ BC = 4
And ∵ BC = 4R & # 178; · sinbsinc = 4
∴R²·=1／·sinBsinC＝－2／[cos﹙B＋C﹚－cos﹙B-C﹚]=2／[1／2＋cos﹙B-C﹚]
When B = C = 60 and 186... Expand
A / Sina = B / SINB = C / sinc = 2R (R is the diameter of ABC circumcircle of triangle)
The area of triangle ABC = 1 / 2 · BC · Sina = √ 3 / 4 · BC = √ 3, ｜ BC = 4
And ∵ BC = 4R & # 178; · sinbsinc = 4
∴R²·=1／·sinBsinC＝－2／[cos﹙B＋C﹚－cos﹙B-C﹚]=2／[1／2＋cos﹙B-C﹚]
When B = C = 60 & # 186; R & # 178; has a minimum value of 4 / 3
In this case, the minimum value of the circumference of the triangle ABC is a + B + C = 3A = 3.2r · Sina = 6.0
If s (n + 1) / Sn = (4N + 2) / (n + 1), find an
From s (n + 1) / S (n) = (4N + 2) / (n + 1), a (n + 1) / S (n) = s (n + 1) / S (n) - 1 = (3N + 1) / (n + 1) can be obtained
S(n)=(n+1)/(3n+1) * a(n+1)
S (n-1) = n / (3n-2) * a (n)
A (n) = (n + 1) / (3N + 1) * a (n + 1) - N / (3n-2) * a (n)
So a (n + 1) / a (n) = 2 (2n-1) / (n + 1) * (3N + 1) / (3n-2),
a(n)/a(n-1)= 2(2n-3)/n * (3n-2)/(3n-5),
.
a(2)/a(1) = 2/1 * 4/1
a(1) = 1.
A (n) = 2 ^ (n-1) * (2n-3) (2n-5)... 3 * 1 / (n!) * (3n-2)
= (2n-2)!/(n!* (n-1)!) * (3n-2).