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Draw the largest circle in a square with a circumference of 16 cm. The area of the circle is a fraction of that of the square
Square area = 4 × 4 = 16 square centimeters
The area of the circle is 2 × 2 π = 4 π = 12.56 square centimeter
12.56/16=157/200
The area of a circle is 157 / 200 of a square
If a and B are non-zero rational numbers, what is the value of a | a | + B | + ab | ab |?
When a ＞ 0, B |a |a || + B | B | B || + ab | ab || ab | = 1 + 1 + 1 + 1 + 1 = 3; when a ＞ 0, B ＜ < 0, a |a |a | + B || + ab |||| + ab | | | |b 124\124\\\\\\\\\\\\124\\ + 1 = - 1
Mathematics application problem, kind person please help me! Beg ~ urgent~
1. Headmaster Tang went to a meeting from a to B by car. It took him 0.75 hours to go because of the rain. How many kilometers are there between a and B? When he returned, it was sunny. Can he get home in 0.5 hours? ^ car: 64 kilometers when he went and 80 kilometers when he returned^
2. A car driver can save 3.22 liters of gasoline a day. It is known that the car uses 1.4 liters of gasoline for driving 10 kilometers. According to this calculation, how many kilometers of gasoline can be saved a day?
It's a whole calculation process
1. The distance between a and B is 0.75 * 64 = 48 km
Because it takes 48 / 80 = 0.6 hours to return
So he couldn't get home in half an hour
2. 1.4/10 = 0.14 L / km
So the gasoline saved in one day can be 3.22 / 0.14 = 23 km
There are two squares, one big and the other small, with a circumference difference of 20 cm and an area difference of 55 square cm
For a process, symbols do not press × + - what, say add subtract multiply divide 4 words on the line!
20 △ 4 = 5cm side length difference
It can be understood that the side length of a square increases by 5 cm and the area increases by 55 square cm
The increased area can be divided into three parts
Two rectangles with sides of 5 cm and a square with sides of 5 cm
Then: 55-5 × 5 = 30 square centimeter
30 / 2 / 5 = 3cm the side length of the original square
3 × 3 = 9 square centimeter
A: the original area of a small square is 9 square centimeters
On signal transmission by electromagnetic wave
Physics books say that in order to use electromagnetic waves to transmit signals, such as sound and television images, electromagnetic waves should be changed with the signals to be transmitted
How to understand this sentence? Why should it change with the signal?
The signal to be transmitted is converted into an electrical signal, and then superimposed with the electromagnetic wave (modulation process), so that the electromagnetic wave changes with the signal to be transmitted, and then the electromagnetic wave carrying the signal to be transmitted is transmitted outward to realize signal transmission. After receiving these signals, the receiving equipment separates these signals from the electromagnetic wave (demodulation process, Also known as detection), and then restore to complete the transmission of the whole signal
The urgent need of acoustics!
When we pour boiling water into the kettle, we can hear the sound from the kettle
Tianxiang thought: what object makes this sound? He guessed that it may be caused by the vibration of the air column in the bottle caused by the impact of water falling from a high place. Do you think there is any other possibility?
It may also be the sound produced by the vibration of the metal shell inside the bottle
The circumference of a rectangle is 120 cm. If the length is reduced by 10 cm and the width is increased by 6 cm, the rectangle will become a square. What is the area of the original rectangle?
Length + width = 120 ÷ 2 = 60cm, let the width of rectangle be x, then the length is 60-xcm, the later length is 60-x-10cm, the later width is x + 6cm, 60-x-10 = x + 6, & nbsp; 50-x = x + 6, & nbsp; & nbsp; & nbsp; & nbsp; 2x = 50-6, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2x = 44, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 22, length: 60-22 = 38 (CM), area: 38 × 22 = 836 (square cm). A: the area of the original rectangle is 836 square cm
How much is the formula 2 and 4 / 5 × 19.5 + 7.2 × 20 and 3 / 4!
2 and 4 / 5 × 19.5 + 7.2 × 20 and 3 / 4
= 2.8 × 19.5 + 7.2 × 20.75
= 54.6 + 149.4
= 204
There should be no easy way to solve this problem
So that's what we have to do
The function f (x) = (A-2) x ^ 2 + (A-2) x-4 has the domain of R and the range of (negative infinity, 0], then the set of a satisfying the condition is
f(x)=(a-2)x^2+2(a-2)x-4
When A-2 = 0,
F (x) = - 4 = not true
a-2
It is known that the length and width of a rectangle are xcm and 3cm respectively
Can you find the area of this rectangle?
In order to distinguish easily, I set the unknowns as a
3a=(3+2)×(a+2)-18
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