The number of a should be at least twice that of B, the number of C should be 5 times that of D, the number of B should be 10 times that of D, and the number of C should be 2 times less than that of B,

The number of a should be at least twice that of B, the number of C should be 5 times that of D, the number of B should be 10 times that of D, and the number of C should be 2 times less than that of B,

A is greater than or equal to 2B
A is greater than or equal to 20
C=5D
B=10D=2C
2C is less than B
D=1,C=5,B=10,

A man took a bamboo raft and floated down the river. He met a speedboat going upstream. He asked the speedboat driver, "is there a ship coming behind you?" The speedboat driver replied, "half an hour ago, I overtook a ship." the bamboo rafts continued to drift down the water for an hour. When they met the oncoming ship, the still water speed of the speedboat was the same as that of the ship______ Times

(1 + 0.5) △ 0.5 = 1.5 △ 0.5 = 3 A: the still water speed of a speedboat is three times that of a ship

The desert area of a certain area in early 2009 is a hectare. Due to natural reasons, the annual desert area will gradually increase at a certain speed. The annual new desert area is 5% of the desert area at the beginning of that year. In order to control the increase of desert area, the region decided to afforest the desert. However, due to the dry climate, the survival area of trees planted in that year is 80% of the planting area, (1) If the desert area in this area is 40000 hectares at the beginning of 2009 and 4000 hectares of trees are planted in this area in 2009, the calculation shows that the desert area in this area at the end of 2009 is increased or decreased compared with that at the beginning of 2009, and the percentage of increase or decrease is calculated. (2) if the desert area in this area is afforested according to the same proportion coefficient K of desert area at the beginning of 2009 and 2011, The desert area at the end of 2010 is reduced by 9.75% compared with that at the beginning of 2009. Please estimate that the desert area at the end of 2011 is the percentage of desert area reduction compared with that at the end of 2010

(1) Original desert area tree planting area desert area at the beginning of 2009: 40000 4000-4000 = 360002009 at the end of 2009: 40000x (1 + 5%) 4000x80% 40000x (1 + 5%) - 4000x80% = 38800 (38800-36000) △ 36000 = 3% (2) a (1 + 5% - 80% k) ^ 2 = (1-9.75%) a → (1 + 5% - 0.8k) ^ 2 = 0.9025

(3) angular function
The length of the base of an isosceles triangle is 20, and its area is (one third of 100 times root sign 3)
What is the vertex angle of this triangle?

Because it is isosceles, the height of the bottom is the middle line
100 times the area
High = (100 / 3 root 3) * 2) / 20 = 10 / 3 root 3
So the bottom corner is a
Tan a = half of high / bottom edge (isosceles triangle line)
Tan a = root 3 of 3
So the base angle a = 30 degrees
Base angle a = base angle B = 30 degrees
Vertex angle = 180-30-30 = 120 degrees

Inverse scale function
four
As shown in the figure, point a is an inverse scale function, y = -, a point on the image, ab ⊥ Y axis is at point B, then what is the area of △ AOB? X

Let a (a, b)
He's on y = 4 / X
So B = 4 / A
A(a,4/a)
AB vertical Y axis
So the ordinates are equal, and the abscissa on the Y axis is 0
So B (0,4 / a)
So ob = | 4 / A|
AB=|a-0|=|a|
So the triangle OAB is a right triangle
So area = ab × ob △ 2
=|a|×|4/a|÷2
=|a×4/a|÷2
=4÷2
=2

The expression of inverse proportion function generally needs several conditions

If you want to determine the expression of an inverse scale function,
Then as long as there is a point coordinate (or a pair of corresponding values of X and y) on the function image,
By substituting the point coordinates (or the corresponding values of X and y) into the expression of the function, the value of K can be obtained,
The expression of the inverse scale function can be determined

As shown in the figure, if the image of an inverse scale function passes through the point m (- 2,1), the expression of the inverse scale function is ()
A. y=2xB. y=-2xC. y=12xD. y=-12x

Let the analytic expression of the inverse proportion function be y = KX (K ≠ 0). It can be seen from the image that the function passes through the point P (- 2,1), ∧ 1 = k − 2, and the analytic expression of the inverse proportion function is y = - 2x

If we know that the image of inverse ratio function y = K / X (K ≠ 0) passes through the point (- 1,2), then the expression of this function is_________ When x

Taking the point (- 1,2) into the equation, we get the following results:
y=-2/x
Because it's a hyperbolic image, when x

If the image of an inverse scale function passes through point P (- 1,5), the expression of the function is___ ．

Let the inverse proportion function be y = KX. Substituting x = - 1 and y = 5, we get k = - 5. Therefore, the answer is y = - 5x

If the image with the inverse scale function y = K / X passes through the point (- 3,4), the inverse scale expression is___ ?

Substituting x = - 3, y = 4 into y = K / x, we get the following result:
k/(-3)=4
k=-3×4= -12
Therefore, the expression of the inverse scale function is y = - 12 / X