As shown in the figure, Xiaogang subtracts a 4cm wide strip from a square piece of paper, and then removes it from the remaining rectangular piece of paper Subtract a strip of 5cm in width. If the area of two strips is exactly the same, what is the area of each strip

As shown in the figure, Xiaogang subtracts a 4cm wide strip from a square piece of paper, and then removes it from the remaining rectangular piece of paper Subtract a strip of 5cm in width. If the area of two strips is exactly the same, what is the area of each strip

Let the side length of a square be X
The area of the first strip is 4x
Second strip area 5 (x-4)
4x=5（x-4）
x=20cm

In △ ABC, its three sides a, B, C satisfy: C ^ 4-2 (a ^ 2 + B ^ 2) C ^ 2 + A ^ 4 + B ^ 4-A ^ 2B ^ 2 = 0, then the size of angle c is

The price of candy a and candy B is 20 yuan / kg and 40 yuan / kg respectively. According to the market survey, the two kinds of candy are mixed according to a certain proportion and sold well. Now the price of candy has been adjusted: the price of candy a has increased by 8%, and that of candy B has decreased by 10%, Then the mixture ratio of a and B should be a: B=______
3：

If the answer is 3:2, your question data is wrong
According to the market survey, the two kinds of candy are sold in a certain proportion and have achieved good sales results. Now the price of candy has been adjusted: the price of a kind of candy has increased by 8%, and the price of B kind of candy has decreased by 10%, Then the mixture ratio of a and B should be a: B=______
Let a take x kg and B take y kg after mixing
20x+24y=20(1+8%)+24(1-10%)
2.4y=1.6x
It is reduced to 2x = 3Y
Then x: y = 3; 2

Take a square paper with an area of 12 square decimeters and cut the largest circle. How many square decimeters is the area of this circle? Please

The side length of the square = the diameter of the circle, the radius of the circle = the side length of the square △ 2, so 12 △ 4 = 3 (square decimeter) is the square of the radius of the circle, so the area of the circle is 3 × 3.14 = 9.42 (square decimeter). A: the area of the circle is 9.42 square decimeter

In the triangle ABC, if AB = AC, CD is perpendicular to AB and D, and CD = half AB, then the angle B is several degrees

Because AB = AC
CD=1/2AB=1/2AC
In △ ACD, CD = 1 / 2Ac
∠A=30°
Because AB = AC
Therefore, B = C = 1 / 2 (180-30) = 75 degree

B is 10km to the east of a and C is 3km to the north of B. now we need to build a road from a to C. along the direction from a to B, the quoted price is 40 million yuan per kilometer. Along other routes, the quoted price is 50 million yuan per kilometer. How to design the most economical route
Using derivative method to solve the problem

Let d be the point on AB, BD = x km
From a to D, (10-x) * 40 million yuan
From D to C, root (x ^ 2 + 9) * 5000
y=(10-x)*4000 + (x^2+9)^(1/2) * 5000
Y '= - 4000 + 5000x / radical (x ^ 2 + 9) = 0
When x = 4, it is the most economical, 6 * 4000 + 5 * 5000 = 49000

The side length of a square sheet of iron is 20 cm. Cut off a rectangle 8 cm wide. The remaining area is 280 square cm. How long is the rectangle cut off

20x20-280=120
Cut off the length of the rectangle = 120 △ 8 = 15 cm

Yang Guang knows that the round light spot under the shade of a tree is the image formed by the sun through the holes between the leaves on the ground. He measured that the diameter of the light spot is 7cm, and the light spot reaches the holes
Yang Guang knows that the round light spot under the shade of trees is the image formed by the sun through the small holes between the leaves on the ground. He measured that the diameter of the light spot is 7cm, the distance from the light spot to the small hole is 7.5cn, and the distance from the sun to the earth is 15 * 10 to the 10th power, then the diameter of the sun is (explain the idea)

According to similar triangles,
Spot diameter 7cm / distance from spot to hole 7.5cn = sun diameter / distance from sun to earth 15 * 10 power
You will calculate the rest

How to understand the definition, expression and determination in physics?

Take resistance as an example. The definition is the ability to block conduction
The expression is r = PL / s
The calculation is r = u / I

The circumference of a rectangle is 30cm. If the length of the rectangle is reduced by 3cm and the width is increased by 2cm, the rectangle will become a square and the area of the rectangle will be calculated

30 △ 2 = 15cm, 10 + 5 = 15cm
10-3=5+2
So it's 10 centimeters long and 5 centimeters wide
Area 10 × 5 = 50 square centimeter