In order to estimate the number of yellow sheep in a certain area, 20 yellow sheep were captured and marked respectively, and then put back. After the marked yellow sheep were completely mixed with the Yellow sheep group, 40 yellow sheep were captured for the second time, and two of them were found to have markers. Therefore, it is estimated that there are yellow sheep in this area______ ．

So the answer is 400

1. The coordinates of the intersection point of the image with the linear function y = k1.x-4 and the positive scale function y = k2.x are (2, - 1)
(1) Let the intersection of the line y = K1 · x-4 with the x-axis and y-axis be a and C respectively; point B is on the line y = K2 · x, and the abscissa is 4, then calculate the area of the quadrilateral ABCO. (o is the origin)
2. Given the point m (6,0) and the point n (x, y) in the first quadrant on the image of the first-order function y = 8-x, let the area of △ omn be s. (1) write the function relation between S and X; (2) find the value range of the independent variable X

1(1)k1=1/2 k2=-1/2 A(4,0) B(4,-2) C(0,-2)
s=2*4=8
2(1)S=6*Y/2 Y=-X+8 S=6*(-x+8)/2=-3x+24
The range of X is 0

A. B, C, D and E are five different integers arranged from small to large. Sum each two of them to get the following 8 sums (there are the same sums among the 10 sums): 17, 22, 25, 28, 31, 33, 36 and 39. Find the average of the five integers

Because a + B is the smallest, a + C is the smallest, D + e is the largest, C + e is the largest, so a + B = 17, D + e = 39, a + C = 22, C + e = 36, we can see that B = C-5, d = C + 3, we can see that B and D are the same odd and even, so B + D is even, in the known conditions, the remaining even number is only 28, so B + D = 28, because B + D = C-5 + C + 3 = 28, so C = 15, then a = 7, B = 10, d = 18, e = 21, the average of five numbers is (7 + 10 + 15 + 18 + 21) △ 5, = 71 △ 5, = 14.2, a: the average of these five integers is 14.2

Given m = 2x ^ 2 + 3x + 4, n = x ^ 2 + 5x + 2. Try to judge the minimum value of m-n

The minimum value is 1, M-N = x & sup2; - 2x + 2 = (x-1) & sup2; + 1

Univariate quadratic equation 2x ^ 2 + (3m-1) x-2m ^ 2 + 3mn-n ^ 2 = 0 (m, n is constant)

"3m-1" in 2x ^ 2 + (3m-1) x-2m ^ 2 + 3mn-n ^ 2 = 0 (m, n is a constant) is wrong, it should be "3m-n", otherwise the title is meaningless. 2x ^ 2 + (3m-n) x - (2m ^ 2-3mn + n ^ 2) = 0 (m, n is a constant) multiply the following cross by 2x ^ 2 + (3m-1) x - (2m-n) (m-n) = 0 (m, n is a constant) and then

In order to make the fraction 3a-2b 2A + B meaningful, what conditions does the letter satisfy?
Can there be many ways to answer this question? Answer 1: 3A ≠ 2B. Answer 2: a ≠ 2B out of 3. Answer 3: B ≠ 3A out of 2
Are all three answers OK?

If the denominator is not zero, 3a-2b is not equal to zero

The value of 1 / 2x ^ 3-1 / 4x + 0.2x ^ 2 + 0.25x-0.5x ^ 3-1 / 5x ^ 2 is independent of X

1/2x³-1/4x+0.2x²+0.25x-0.5x³-1/5x²
=(1/2x³-0.5x³)+(0.2x²-1/5x²)+(-1/4x+0.25x)
=0
∵ no matter what value x takes, the value of the algebraic expression is equal to 0
The value of an algebraic expression is independent of X

It is proved that the determinant of the transposed adjoint matrix of a is equal to zero

To the contrary
If | a * | ≠ 0
Then a * is reversible
From AA * = | a | e = 0, a = AA * (a *) ^ - 1 = 0
So a * = 0, which is in contradiction with | a * = 0
So | a * | = 0

The square of 2x - 5x = 1 is solved by formula method

2x²-5x-1=0
a=2,b=-5,c=-1
So △ = B & # 178; - 4ac = 33
So x = (5 - √ 33) / 2, x = (5 + √ 33) / 2

When the absolute value a = 2, the absolute value b = 3 and a times B is less than 0, we can find the value of the square of a, the third power of B / 12

Because A.B