China's area is 9.6 million square kilometers. What's the concept? How big is a square kilometer? Give me a more detailed analogy and calculation

China's area is 9.6 million square kilometers. What's the concept? How big is a square kilometer? Give me a more detailed analogy and calculation

One square kilometer is one kilometer long and one kilometer wide. One square kilometer is 1500 mu of land. China has 14 billion mu of land, excluding the sea area

How to express tax rate by formula

Generally, a specific industry has a specific tax category, and each tax category is generally a specific tax rate (unless it is individual income tax and other taxes that adopt excessive progressive tax rate), otherwise, can the tax rate still be expressed by formula? It's really hard to understand

180 degrees - 52 degrees 18 minutes 36 seconds - 25 degrees 36 seconds * 4 =?
The third is 36 seconds, not minutes

180 degrees - 52 degrees, 18 minutes, 36 seconds - 25 degrees, 36 minutes, multiplied by 4
=180 degrees - (52 degrees, 18 minutes, 36 seconds + 25x4 degrees, 36x4 minutes)
=180 degrees - (152 degrees 162 minutes 36 seconds)
=177 degrees 179 minutes 60 seconds - (152 degrees 162 minutes 36 seconds)
=25 degrees, 17 minutes, 24 seconds

If the line passing through point P (2,2) is known to be tangent to circle (x-1) 2 + y2 = 5 and perpendicular to line ax-y + 1 = 0, then a = ()
A. −12B. 1C. 2D. 12

Because point P (2,2) satisfies the equation of circle (x-1) 2 + y2 = 5, the line passing through point P (2,2) is tangent to circle (x-1) 2 + y2 = 5 and perpendicular to the line ax-y + 1 = 0, so the line connecting the tangent point and the center of the circle is parallel to the line ax-y + 1 = 0, so the slope of the line ax-y + 1 = 0 is a = 2 − 02 − 1 = 2

What's 5 out of 9 multiplied by 11
I'm stupid. No. help! How much is 5 / 9 times 11

5 out of 9 times 11 is 55 out of 9

X ^ 2-4x = 1, then what is x ^ 3-x ^ - 3? The correct answer is 322, how to calculate

A: x ^ 2-4x = 1
Divide both sides by X to get x-4 = 1 / X
x-1/x=4
So: x ^ 3-1 / x ^ 3
=(x-1/x)(x^2+1+1/x^2)
=4*[(x-1/x)^2+3]
=4*(4^2+3)
=4*19
=76
322 is wrong

How to simplify

√16-√81
=4-9
=-5
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How to judge the size of quadratic function ABC

A is to determine the opening direction of quadratic function, a > 0, opening up, a "0, opening down; after a is determined, look at the symmetry axis over there, a and B jointly determine (the symmetry axis is - B / (2a)), let x = 0, the intersection of function on Y axis is the size of C

Simple calculation: 2346 × 3455-2345 × 3456

2346×3455-2345×3456=2346×3455-（2346-1）×3456=2346×3455-2346×3456+3456=3456-2346×1=3456-2346=1110

Given the set M = {- 1, 1}, n = {x | 1 ≤ 2x ≤ 4}, then m ∩ n=______ ．

∵ n = {x | 1 ≤ 2x ≤ 4} = {x | 0 ≤ x ≤ 2} and ∵ M = {- 1, 1}, ∩ n = {1}