A cuboid, the bottom is a cube, the height is 18 cm, the side expansion is a rectangle, the length is twice the width, find the cuboid volume

A cuboid, the bottom is a cube, the height is 18 cm, the side expansion is a rectangle, the length is twice the width, find the cuboid volume

The length is twice the width, that is, the perimeter of the square is twice the height, so the perimeter of the square is 18 * 2 = 36, and the side length is 36 / 4 = 4
So the volume is 4 * 4 * 18 = 288

A cuboid is just cut into two cubes, and the surface area increases by 18 square meters. What is the volume of this cuboid

Surface area increase 18 square meters = the area of two squares, so a square = 18 / 2 = 9 square meters, side length = 3 meters
Then the length of the cuboid is 2 * 3 = 6m, and the width and height are 3M
So volume = 6 * 3 * 3 = 54 cubic meters

A cuboid can just be cut into two cubes. After it is cut, its surface area increases by 18 square meters. How large is its volume
Expression

1. 18 divided by 2 equals 9 (square meters)
Is the area of one face of a cube
2. 9 divided by 3 equals 3 (meters)
Square root, 3 is the edge length of cube
3. Three times three times three equals nine (cubic meters)
The area of a cube
4. 9 times 2 equals 18 (cubic meters)
Cuboid volume
A: its volume is 18 cubic meters

The area of a rectangle and a square is 1225cm2, and that of a circle is 1256cm2? Which is the smallest? If the areas of these three figures are equal, can you find the size relationship between their girths?

The area of a rectangle and a square is 1225cm2, and that of a circle is 1256cm2. The maximum perimeter of the three figures is rectangle, and the minimum is circle. When the area of the three figures is equal, the relationship of their perimeter is reversed, that is, rectangle > square > circle

If a square with an area of 32 square meters is reduced by 2:1, the perimeter of the square is () cm

Let the area of the reduced square be x square meters, then 32: x = 2: 1, x = 16, so its side length is 4 meters, and its perimeter is 4x100x4 = 1600 cm

It is known that the circumference of the circle is 1cm and the area is the square of SCM
(1) Finding the functional relation between S and 1
(2) When s = π, find the circumference of the circle
(3) When 1 takes what value, s is greater than or equal to 9 π?

It should be the lowercase letter L of L, not 1
1、s=π*(l/2π)²=l²/(4π)
2、s=π=l²/(4π)
∴l=2π
s>=9π
l²/(4π)>=9π
l²>=36π²
l>=6π

In the interval [12,2], if the function f (x) = x2 + BX + C (B, C ∈ R) and G (x) = x2 + X + 1x have the same minimum value at the same point, then the maximum value of F (x) in the interval [12,2] is ()
A. 134B. 4C. 8D. 54

G (x) = x2 + X + 1 x = x + 1 x + 1 ≥ 3, if and only if x = 1, the equal sign holds, and the vertex coordinates of the function f (x) = x2 + BX + C are (1,3), x = − B2 = 11 + B + C = 3, then B = - 2, C = 4, f (x) = x2-2x + 4, f (x) max = f (2) = 4

If f (x) = x & sup2; + BX + C, and f (1) = 0, f (3) = 0, find the value of B and C; try to prove that the function f (x) is an increasing function in the interval (2, + ∞)

1,3 are two of F (x) = 0, so B = - 4, C = 3 (Veda's theorem)
Any 2

It is proved that the quadratic function f (x) = AX2 + BX + C (a > 0) is an increasing function in the interval (- ∞, - B / 2a)
If you do have a step of a (x1 + x2) + b > 0, then I want to know how this step comes from?
Also, do you want to do a lot of math problems for a long time, and then you will establish a mathematical thinking, and is this thinking very important for learning math? Do you think what I said is right? If not, please advise me

It is proved that the quadratic function f (x) = AX2 + BX + C (a > 0) is an increasing function in the interval (- ∞, - B / 2a)
5 - 14 days and 23 hours to the end of the problem
If you do have a step of a (x1 + x2) + b > 0, then I want to know how this step comes from?
Question supplement: also, I would like to ask, do you want to do a lot of math problems for a long time, and then establish a mathematical thinking, and this thinking is very important for learning mathematics, do you think what I said is right? If not, please advise me
answer:
【1】
Method 1: use the derivation method learned in senior two
Let f '(x) = (AX ^ 2 + BX + C)' = 2aX + b > 0
Then x ∈ (- ∞, - B / 2a) is an increasing function. Is it simple?
Method 2: the simplest and most primitive definition
Let x1, X2 ∈ (- ∞, - B / 2a) x1

The perimeter of a rectangle is 30cm. If you reduce its length by 3cm and increase its width by 2cm, it will become a square. Find the area of the square

From the meaning of the title:
Length is 3 + 2 = 5cm more than width
The width of a rectangle
=（30-5×2）÷4
=20÷4
=5 cm
Namely: square side length = 5 + 2 = 7 cm
Square area
=7×7
=49 square centimeters