21 out of 28 is 3 out of 56

21 out of 28 is 3 out of 56

21 out of 28 equals 3 out of 4 and 3 out of 56 equals 168 out of 56

- 3.92 + 6.47 - (+ 8.56) - (- 4.28)?

In this way, (3.92 + 8.56) + (6.47 + 4.28)

The zeros of the function f (x) = lgx SiNx in the domain (0, + ∞) have______ One

The zero point of function f (x) = lgx SiNx is the root of equation lgx SiNx = 0, that is, the root of equation lgx = SiNx, let Y1 = lgx, y2 = SiNx, make the image of the above two functions, as shown in the figure, ∵ when x = 5 π 2, lg5 π 2 < 1, when x = 9 π 2, lg9 π 2 > 1

Given a (- 2,0), B (1,5) and vector a = (x, 2), and vector ab ‖ vector a, then x=
A 5 / 3 B C D 5 / 6

The slope of AB is 5 / 3. Because it is parallel to vector a, the slope of vector a is 5 / 3, that is, 2 / x equals 5 / 3

Finding the number of zeros of function y = ln (x-1) + 0.01x

1
When the function monotonically increases and x = 1 + 1 / E, fX0
So there's only one zero

If the maximum value of the function y = - x2-2x + 3 in the interval [a, 2] is 15 / 4, then a is equal to ()

Function opening down
And the symmetry axis is - B / 2A = - 1
f(-1)=-1+2+3=4
15/4-1
The maximum value is f (a)
f(a)=-a^2-2a+3=15/4
a^2+2a+3/4=0
4a^2+8a+3=0
△=16
a=(-8±4)/8
A = - 1 / 2 or - 3 / 2
There is a > - 1
Then a = - 1 / 2

The known function f (x) = LG (x ^ 2 + 2x + a) / x x belongs to (0, +)
Finding the minimum value of function f (x) when a = 1 / 2
If any x belongs to [1, +, f (x) constant, it is meaningful to try to find the value range of real number a

1) Because LG function is monotonically increasing, and (x ^ 2 + 2x + a) / x gets the minimum value when x = 1 / 2, that is, f (x) = 2 + √ 2
2) Meaningful is (x ^ 2 + 2x + a) / x > 0
It holds when a > = o
When A-2. Because x > = 1. So a > - 3
So a > - 3

On some mathematical problems of rational numbers,
1. Sort positive rational numbers: 1 / 1 2 / 1 1 / 2 3 / 1 2 / 2 4 / 1 3 / 2 2 / 3 1 / 4 The serial number of 1995 / 1994 is__________
2. When x=___ The formula 3 + | x-4 | has a minimum value, and the minimum value is_____
3. Subtract one-half of 2010, then the remaining one-third, then the remaining one-fourth, and then the remaining one-fifth. By analogy, we know that the final result is ()
A.4 B.3 C.2 D.1
4. Calculation: 1-3 + 5-7 + 9-11 + +97-99=_______
What is the serial number of the first question?
And the second question, what if x is negative?

1 1999
2 4 3
3 D
4 -50

All rational numbers can be represented by points on the number axis

According to the meaning of the number axis, real numbers and the points on the number axis are corresponding one by one, so all rational numbers can be represented by the points on the number axis, so the answer is correct

Given that the equation 4 (x + 2) - 3 = ax about X has no solution, find the value of A
The equation 2 (X-B) = ax + 5 for X is known
When a____ ,b_____ The equation has a unique solution;
When a____ ,b_____ The equation has no solution;
When a____ ,b_____ The equation has innumerable solutions

4 (x + 2) - 3 = ax, 4x + 8-3 = ax, (4-A) x = - 5, if there is no solution, then 4-A = 0, then a = 4
On the equation 2 (X-B) = ax + 5 of X
2x-2b=ax+5
(2-a)x=5+2b
If the equation has a unique solution, then 2-A ≠ 0, then a ≠ 2, and B can take any value
If the equation has no solution, then 2-A = 0,5 + 2B ≠ 0, then a = 2, B ≠ - 5 / 2
If the equation has innumerable solutions, then 2-A = 0,5 + 2B = 0, then a = 2, B = - 5 / 2