Calculation: (x + 2Y) (X-Y) - (x + y) ^ 2

Calculation: (x + 2Y) (X-Y) - (x + y) ^ 2

(x+2y)(x-y)-(x+y)^2
=x^2-xy+2xy-2y^2-x^2-2xy-y^2
=-xy-3y^2

Calculation: (x-2y) (x2-4y2) (x + 2Y)

The original formula = (x-2y) (x + 2Y) (x2-4y2) = (x2-4y2) (x2-4y2) = x4-8x2y2 + 16y4

4Y-2Y=1.2
000000

4Y-2Y=1.2
2Y=1.2
Y=0.6

What is the quotient of the sum of five quarters and its reciprocal divided by the difference between five quarters and its reciprocal

(5/4+4/5)/(5/4-4/5)=(9/20)/(1/20)=9

There are 6 liters of 18 ℃ water in the container, and 8 liters of water should be injected to make the mixed water in the container not lower than 30 ℃ and not higher than 36 ℃. What should be the temperature range of 8 liters of water injected

The injection temperature of 8 cubic decimeter is X,
Then 30 ≤ (18 * 6 + 8x) / (6 + 8) ≤ 36
39≤x≤49.5

There's six liters of water at 18 degrees in the container,
Now we need to inject 8 liters of water into it, so that the temperature of the mixed water is not lower than 30 degrees and not higher than 36 degrees. What is the temperature range of the injected 8 liters of water?

Let the temperature of 8 liters of water be t
Q discharge = q suction
According to q = MC △ t
8kg * C water * (T-30 ℃) = 6kg * C water * (30 ℃ - 18 ℃) - t = 39 ℃
8kg * C water * (t-36 ℃) = 6kg * C water * (30 ℃ - 18 ℃) - t = 45 ℃
So the temperature of 8 liters of water should be in the range of 39 to 45 degrees

A glass of water temperature from 30 degrees to 10 degrees, then, how can the glass of water change?

Temperature is the embodiment of the average kinetic energy of molecules, while the average kinetic energy of temperature polymer is larger, and the internal energy is equal to the sum of the molecular kinetic energy and the molecular potential energy. Therefore, when water is cooled, because the volume of water does not change significantly, that is, the molecular potential energy does not change significantly, and the average kinetic energy of molecules will decrease, the internal energy of water will decrease

Mix 100 ml of 80 ℃ water with 250 ml of 40 ℃ water. What is the amount of water and the temperature?

The amount of water is 100 + 250 = 350 ml
The temperature is t
100c（80-t）=250c（t-40）
800-10t=25t-1000
35t=1800
T = 51.43 degrees

The reduction ratio is 12.56:18.84=
process

12.56:18.84=1256/100:1884/100=1256:1884=314:471

Fill in the appropriate operation symbols (+, -, ×, △) in each box to make the following equations hold 2 □ (- 4) □ (- 6 □ (- 8)
2□（﹣4）□6□（﹣8）=0
﹣8□（﹣2）□（﹣4）□（﹣6）=2

In fact, it's very simple, just need to calculate!
The first one: 2 + (- 4) - 6 - (- 8) = 0
-2-6 + 8 = 0, i.e. - 8 + 8 = 0
The second: - 8 ÷ (- 2) - (- 4) + (- 6) = 2
That is 4 + 4-6 = 2