If the equation x 2 - ax + a 2 - 4 = 0 about X has two positive real roots, find the value range of A

If the equation x 2 - ax + a 2 - 4 = 0 about X has two positive real roots, find the value range of A

∵ the equation x2-ax + A2-4 = 0 has two positive real roots, which can be set as x1, X2, then x1 ＞ 0, X2 ＞ 0 ∵ satisfies the condition △ = A2 − 4 (A2 − 4) ≥ 0x1x2 = A2 − 4 ＞ 0x1 + x2 = a ＞ 0, that is, A2 ≤ 163a ＞ 2 or a ＜− 2A ＞ 0, the solution is 2 ＜ a ≤ 433, that is, the value range of a is (2433]

Given that the function f (x) = χ & # 179; + a χ & # 178; + χ + 1 is an increasing function on (- ∞, 1), try to find the value range of A
Given that the function f (x) = χ & # 179; + a χ & # 178; + χ + 1 is an increasing function on (- ∞, 1), try to find the value range of a, I do not do the same as the answer, I calculate a ＞ - 2, the answer is [- √ 3, √ 3]
When to use Δ greater than 0 or less than 0 solution, when to take numbers

If f '(x) = 3x ^ 2 + 2aX + 1, f' (x) > = 0 is an increasing function on (- infinity, 1]

If the inequality x-2ax + 1 > 0 holds on [1,3], the range of a is obtained
Is x ^ 2-2ax + 1 > 0! dial the wrong number

2x-2ax+1>0
2x(1-a)>-1
Because x is a positive number
So 1-A > - 1 / 2x
a-1

Solution equation: 23x = 14x + 14

23x=14x+14
23x-14x=14
9x=14
x=14/9

In the plane rectangular coordinate system, the set C = {(x, y) / y = x} represents the straight line y = X. from this point of view, what does the set D = {(x, y) / {2x-y = 1, x + 4Y = 5} represent? What is the relationship between the set C and D? How to calculate the intersection coordinates of the set D is the point (1,1)

The intersection point (1,1) of two lines 2x-y = 1, x + 4Y = 5 is on y = x, so D is a subset of C

Let X & # 178; - 6x + m be a perfect square, then M=_______

9, the square of (x-3) = the square of X - 6x + 9

Given three vertices a (1,1) B (5,3) C (4,5) of triangle ABC, a point m on edge AB, vector am = 3, vector MB, P is edge AC
Given three vertices a (1,1) B (5,3) C (4,5) of triangle ABC, a point m on the side of AB and vector am = 3, vector MB, P is a point on the side of AC, if the area of triangle APM = 1 / 2 triangle ABC, find the ratio of P-component vector AC

The solution can use the analytic method to solve the equations, which is more troublesome
First, find the length of the three sides of the triangle
AB = radical 20; BC = radical 5; AC = 5
It can be seen that AC = AB + BC
Then the triangle ABC is a right triangle with angle B = 90 degrees
Triangle ABC area = 1 / 2 * radical 20 * radical 5 = 5
Given am = 3MB, then am = AB * (3 / 4) = radical 20 * (3 / 4)
Let Mn be perpendicular to AC and N, because the triangle amn is similar to ACB
Then am / AC = Mn / BC
MN=AM*BC/AC=3/2
Triangle APM area = 1 / 2 * AP * nm = 3 / 4 * AP = 1 / 2 triangle ABC = 5 / 2
So AP = 10 / 3
PC=AC-AP=5-10/3=5/3
That is, the ratio of the P-component vector AC is AP / PC = 2 / 1

Absolute value comparison size (using absolute value comparison and writing process) is minus two fifths and minus three fourths
Online, etc!!!! fast

Because the absolute value of minus two fifths = two fifths
Absolute value of minus three fourths = three fourths
2 out of 5 is less than 3 out of 4
So negative two fifths is greater than negative three fourths

When the rice cooker starts to cook, calculate the number of turns of the turntable,
It is found that: the watt hour meter first turns 100 turns faster, then turns 20 turns slower, and then stops the power supply
The parameter of the meter is "220 V 10 (20) a 600 revs / kWh"
Ask: the work that electric energy does through electric cooker

600revs / kWh on the electric energy meter indicates that the electric energy consumed by the electric appliance is 1kwh per 600 revolutions of the turntable of the electric energy meter. Now the electric energy meter has turned 120 revolutions, and the total energy consumed is w = 120 / 600 = 0.2kwh = 720000j

Given the set a = {x | x2-9 ≤ 0}, B = {x | x2-4x + 3 ＞ 0}, find a ∪ B, a ∩ B

For the set a: x2-9 ≤ 0, it is reduced to (x-3) (x + 3) ≤ 0, and the solution is - 3 ≤ x ≤ 3, and the set a = [- 3, 3]; for the set B: x2-4x + 3 > 0, it is reduced to (x-3) (x-1) > 0, and the solution is 3 < x or x < 1, and the set B = (- ∞, 1) ∪ (3, + ∞); ∪ a ∪ B = [- 3, 3] ∪ (- ∞, 1) ∪ (3, + ∞) = R; a ∩ B = [- 3, 3] ∩ [(- ∞, 1) ∪ (3, + ∞)] = [- 3, 1]