To judge a proposition, if a > 0, then the bisection of a > the true or false of A. if it is a true proposition, please prove it. If it is a false proposition, please give a counter example

If AA, so if a > 0, the square of a is greater than a is a false proposition

Judge whether the following propositions are true or false. If they are false, please give counter examples. If X & # 178; Y0, y

This is a false proposition for the following reasons:
If for any real number x, y satisfies:
x^2y0,y

When a batch of cement is delivered to the construction site, one quarter of the cement is used on the first day, and one third of the cement is used on the second day. There are 120 tons left. How many tons are there in total?

Total = 120 (1-1 / 4-1 / 3) = 288 tons

It is known that the length of three sides of a triangle is three continuous non-zero natural numbers. If the maximum angle is twice the minimum angle, the length of three sides can be obtained

Junior high school students: let C = 2b in ABC and CD be the angle bisector, then ABC is similar to ACD. Let CD be the solution to the equation. Senior high school students: let the minimum angle of a triangle be a, and the lengths of three sides be k-1, K, K + 1 respectively. According to the sine theorem and the known (k-1) / Sina = (K + 1) / sin2a = (K + 1) / 2sinacosa ∫ cosa = (K + 1) / (2k-2) and ∫ C ∫

For the allocation of a concrete, cement, sand gravel ratio is 2:3:7, three kinds of materials are 120 tons, when the stones used up, the other two kinds of materials to save how much

Cement surplus 120-2 * 120 / 7T yellow sand surplus 120-3 * 120 / 7T

Let a = f (0), B = f (2), C = f (- 1), then ()
A. a＜c＜bB. a＜b＜cC. b＜c＜aD. c＜b＜a

Solution; ∵ function y = f (x) is an even function, ∵ function f (x) is symmetric about y-axis, and y = f (x) is shifted 2 units to the right to get y = f (X-2), ∵ y = f (X-2) monotonically decreases on [0,2], ∵ y = f (x) monotonically decreases on [- 2,0], then f (2) = f (- 2), ∵ f (0) < f (- 1) < f (- 2), that is, a < C < B, so select: a

There are 150 people in the first workshop of the clothing factory, which is 57% of the number in the second workshop. The number in the two workshops is just 67% of the total number of workers in the whole factory. How many workers are there in the whole factory?

A: there are 420 workers in the factory

If x, y ∈ R and X2 + y2 = 1, then the minimum value of (1-xy) (1 + XY) is_ , the maximum value is_ ．

From the meaning of (1-xy) (1 + XY) = 1-x2y2, ∵ x2 + y2 = 1 ≥ 2x2y2, ∵ x2y2 ≤ 14, - x2y2 ≥ - 14, ∵ 1-xy (1 + XY) = 1-x2y2 ≥ 1-14 = 34, and ∵ x2y2 > 0, ∵ 1-x2y2 ≤ 1, ∵ the minimum value of (1-xy) (1 + XY) is 34, the maximum value of (1-xy) (1 + XY) is 34

How many different ways are there to choose a monitor and Deputy monitor from four boys and five girls? (monitor and Deputy monitor must be matched by boys and girls)

4 × 5 = 20 (species) a: there are 20 different selection methods

Given 2x = 3Y, find the value of XY / XX + yy yy / XX YY

2/9

To judge a proposition, if a > 0, then the bisection of a > the true or false of A. if it is a true proposition, please prove it. If it is a false proposition, please give a counter example