The geometric meaning of Dy (differential) is the change of slope. What is the geometric meaning of DX? Is it △ x?

The geometric meaning of Dy (differential) is the change of slope. What is the geometric meaning of DX? Is it △ x?

Dy / DX is the variable that represents the slope. It is obvious that Y / X represents the slope, and Dy DX represents the change value of ordinate and abscissa respectively

The tangent equation of curve y = 2x2 + 1 at point P (- 1,3) is ()
A. y=-4x-1B. y=-4x-7C. y=4x-1D. y=4x+7

When x = - 1, the tangent equation of the curve y = 2x2 + 1 at point P (- 1,3) is Y-3 = - 4 (x + 1), that is y = - 4x-1, so a

What is the physical meaning of Maxwell's equations (differential form) in electrodynamics?
Be brief and to the point~

1. The time-varying electric field has rotation and dispersion, and the power line can be closed or not
2. The time-varying magnetic field has rotation but no divergence, and the magnetic lines of force are always closed
3. Unclosed power line is from positive charge to negative charge; closed power line intersects magnetic line; closed magnetic line intersects either power line or current
4. In the passive region, both the time-varying electric field and the time-varying magnetic field are rotating and non dispersing
5. Due to the mutual excitation of electric field and magnetic field, electromagnetic wave can be formed and propagated to space at limited speed

The proof of Morgan's theorem is not a graph method
It's best to use the basic laws of logic algebra to prove!
It is better to upload the proof process with a screenshot of word formula

Please refer to the picture. Please prove the second one by yourself

The two trains run from 580 kilometers away and meet after 2.5 hours. It is known that the speed ratio of the two trains is 14:15
What is the speed of each column and explain clearly, thank you

Two cars in one hour, a total of 580 △ 2.5 = 232 km
therefore
The speed of a is 232 × 14 (14 + 15) = 112 km / h
B the speed is 232-112 = 120 km / h

If the average of three numbers is 40 and their ratio is 4:7:9, then the three numbers are______ 、______ 、______ ．

4 + 7 + 9 = 2040 × 3 × 420 = 2440 × 3 × 720 = 4240 × 3 × 920 = 54 A: the three numbers are 24, 42 and 54 respectively

The sum of five consecutive even numbers is 170. What are the five even numbers

In the middle is 170 △ 5 = 34
So 30, 32, 34, 36, 38

A number is composed of 800 million, 3 million, 5 100000 and 4 tens______ , omit the mantissa after "100 million"______ 100 million

(1) (2) 803500040 ≈ 800 million, so the answer is: 803500040, 8

On a map with a scale of 1:5000000, the distance between a and B is 5cm. Draw it on another map with a scale of 1% of 2500000

Set: the actual distance is x cm 1 / 5 million = 5 / x, x = 25 million, set the distance on the two maps as y cm 1 / 2.5 million = Y / 25 million, y = 10. Answer: the distance on the two maps is 10 cm

A problem of Cauchy inequality
If a + B + C + D = 6, a ^ 2 + B ^ 2 + C ^ 2 + D ^ 2 = 12, the maximum value of D is~

Just separate D
a+b+c=6-d,a^2+b^2+c^2=12-d^2
From Cauchy inequality
（1+1+1）（a^2+b^2+c^2）>=(a+b+c)^2
So 3 (12-d ^ 2) > = (6-D) ^ 2
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