1 / 2, 1 / 4, 1 / 6, 1 / 8, the number of 2013 is

1 / 2, 1 / 4, 1 / 6, 1 / 8, the number of 2013 is

It should be one in 2026

It is known that the circumference of isosceles triangle is 20cm. Let the base length be y and the waist length be X. find the functional relationship between Y and X, and find the value range of the independent variable x

∵ 2x + y = 20, ∵ y = 20-2x, that is, x < 10, ∵ the sum of the two sides is greater than the third side, ∵ x > 5. To sum up, we can get 5 < x < 10

Verification: 1 / A + 1 / B + 1 / C ≥ 9
It is known that a, B and C belong to R, and a + B + C = 1

(1/a+1/b+1/c)*(a+b+c)=3+b/a+a/b+c/a+a/c+c/b+b/c
B / A + A / b greater than or equal to 2
C / A + A / C greater than or equal to 2
C / B + B / C greater than or equal to 2
So 1 / A + 1 / B + 1 / C is greater than or equal to 9 if and only if a = b = C = 1 / 3
Like this question oneself tries under, next time will be able to!

There is a point O in parallelogram ABCD, connecting do, Co, Ao, Bo, ask s triangle AOB + s triangle cod = s triangle AOD + s triangle cob?
I'm sorry, I can't get the picture. This is actually the question that the rich man gave his son the land
There are pictures in this one

First, make height to 4 sides through point 0
OE⊥AB OF⊥BC OM⊥CD ON⊥DA
Because it's a parallelogram
So OE and OM are on the same line
Similarly, of and on are on the same line
The area formula is: bottom * height / 2
S△AOB+S△COD=AB*OE/2+CD*OM/2=AB*(OE+OM)/2 (AB=CD)
S△AOD+S△COB=BC*OF/2+AD*ON/2=BC*(OF+ON)/2 (BC=OD)
Because when AB or CD is the bottom, OE + OM is the height of parallelogram
When BC or Da is the bottom, of + on is the height of parallelogram
So s △ AOB + s △ cod = AB * (OE + OM) / 2 = s parallelogram / 2
S △ AOD + s △ cob = BC * (of + on) / 2 = s parallelogram / 2
So s △ AOB + s △ cod = s △ AOD + s △ cob
It's hard work

-1 ＜ lgx ＜ 1, find the range of X

1/10＜x＜10

There is a rope and a bamboo pole. When the rope is folded in half, it is 2 meters longer than the bamboo pole. When the rope is folded in four, it is 2 meters shorter than the bamboo pole. How long are the bamboo pole and the rope?

Rope: (2 + 2) △ 12-14, = 4 △ 14, = 16 (m); bamboo pole: 16 × 12-2, = 8-2, = 6 (m); answer: rope is 16 m long, bamboo pole is 6 m long

Given 2A + B = (- 4,3), a-2b = (3,4), find the value of a · B

What's your solution? First of all, multiply Formula 1 by 2 and add formula 2 to get a vector (- 1,2), then find B vector (- 2,1), and then find the vector dot multiplication to get the answer as 0

A triangle with a base of 4cm and a height of 2cm. How much is the base and height after enlarging by 2:1

The bottom has become 8 and the height has become 4. This is the expansion according to the shape. After the expansion, the shape does not change. Therefore, the bottom and the height should be doubled

If a + B = 5 and a > 0, b > 0, then log (1 / 2) (AB ^ 2) has ()
A. Minimum - 2
B. Maximum - 2
C. Minimum log (1 / 2) (500 / 27)
D. Maximum log (1 / 2) (1000 / 27)

a+b=5
The third root of a + B / 2 + B / 2 ≥ 3 * (a * B ^ 2 / 4)
The third root of 5 ≥ 3 * (a * B ^ 2 / 4)
125/27≥ab^2/4
500/27≥ab^2
Because the base 1 / 2 is less than 1
The function log (1 / 2) x is a decreasing function, so
log(1/2)(ab^2)≥log(1/2)(500/27)

Make a cuboid uncovered water tank with a volume of 256 cubic meters and a square bottom. What is the side length and height of its bottom? It is the most economical material
Finding monotone interval and extremum of function y equal to cubic x minus square x plus 1

x²h＝256
S＝x²+4xh＝x²+2xh+2xh
X & # 178; × 2xh × 2xh = 4 (X & # 178; H) &# 178; = 4 × 256 & # 178; (constant)
In this case, H = 4, x = 8, s = 192 (M2)