A 56 meter long fence is used to form a rectangular flower bed (length and width are the whole centimeter). One side of the fence is used. How to make the area of the rectangular flower bed the largest Seeing your answer, I want to ask how the fourth equal sign suddenly came up with a 392, where did it come from

A 56 meter long fence is used to form a rectangular flower bed (length and width are the whole centimeter). One side of the fence is used. How to make the area of the rectangular flower bed the largest Seeing your answer, I want to ask how the fourth equal sign suddenly came up with a 392, where did it come from

As we know, if the circumference is a rectangle, it must be the square with the largest area. If the length is x and the width is y, then there is 2x + y = 56. To make the figure as square as possible, we must make 2x = y, so there is x = 14, y = 28,

R square + R square; why is it equal to √ 2R? I'm not very good at math,
How much is r square + R square under the root sign? How do you calculate that?

R squared equals 2R
So the root 2R squared is to square 2, square r squared
Multiply by √ 2R
So r square + R square under the root sign is equal to √ 2R

How much is the square of 15 plus 55?

280

The process of solving the problem that the square of (x-1) is equal to 3

（x－1）²＝3
x－1＝±√3
x＝±√3+1

How much is the square of (- 1) ten × 2 + (- 2) three △ 4

Square of (- 1) ten × 2 + (- 2) three △ 4
=1x2-8÷4
=2-2
=0
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How much is the square of 9 (x-3) equal to 4 (x + 6)

9(x-3)^2=4(x+6)^2
3 (x-3) = 2 (x + 6) or 3 (x-3) = - 2 (x + 6)
3x-9 = 2x + 12 or 3x-9 = - 2x-12
X = 21 or x = - 3 / 5

K (the square of 3K - 6K + 1) = 2, what is k equal to

k(3k²-6k+1)=2
3k³-6k²+k-2=0
3k²(k-2)+(k-2)=0
(k-2)(3k²+1)=0
K = 2

Carpet a 2.5 m long, 2 m wide and 3.2 m high right angle staircase

Area = (2.5 + 3.2) × 2 = 11.4 square centimeter

There are several ladders in Xiaolin's stairs. He measured that the horizontal width of the stairs is AC = 4 meters and the slope is 5 meters. He wants to lay a carpet. The carpet is 20 yuan per meter. How much will she prepare

According to Pythagorean theorem, the sum of squares of two right angle sides is equal to the square of hypotenuse. The height of staircase is 3M. The length of carpet is 4m + 3M. 7 * 20 = 140 yuan

The hotel is going to lay red carpet on the main staircase of the hall. It is known that the price of red carpet is 30 yuan per square meter. The width of the main staircase is 2.5 meters. The side is 1 meter and the bottom is 5.5 meters long. How much does it cost for the hotel to buy this kind of carpet?

3.1 * 2.5 + 5.5 * 2.5 = 21.5 square meters
21.5 * 30 = 645 yuan