Operation and simplification of logical expression

The operators in C expression are combined according to the priority order. The priority order of operators in this expression is: (),%, = =,! =, & &, |
So the expression calculation is decomposed into:
temp1=year%4;
temp2=year%100;
temp3=year%400;
temp4=(temp1==0);
temp5=(temp2!=0);
temp6=(temp3==0);
temp7=(temp5&&temp6);
expr=(temp7||temp6);
Therefore, the operands of the operator "! =" are temp2 and 0, namely (year% 100) and 0 expressions;

In the following Visual FoxPro expression, the result is logical, which is true
A) EMPTY(.NULL.) B) LIKE(‘xy?’,‘xyz’)C) AT(‘xy’,‘abcxyz’) D) ISNULL(SPACE(0))

The answer is B
A) . f.empty() is a null function, where null refers to carriage return, line feed, empty string, numeric value 0, etc., not null. Function isnull (null) =. T
B) . t. like() is a string comparison function. If it is exactly the same, it will be true. Here? Is a wildcard and can be Z
C) Returns the position of a string at the first occurrence of two strings. If it does not appear at any one time, it returns 0
D) The. F. isnull (expression) function is true if and only if the expression = null, and all others are false

The logical algorithm in the following expression is
A.C•C=C2 B.1+1=10 C.0

In the space quadrilateral oabc, G and H are the center of gravity of triangle ABC and triangle OBC respectively. Let OA = A and ob = b be vectors
In the space quadrilateral oabc, G and H are the center of gravity of triangle ABC and triangle OBC respectively. Let OA = vector a, OB = vector B, OC = vector C
Use vector a, vector B, vector C to represent vector og and vector GH

There is no problem with the problem alone

The two piles of yellow sand are 5.7 tons in total, three quarters of which are used in the first pile and three fifths in the second pile,
Put the rest of the two piles together, one fifth less than the first pair. How many tons was the first pile
We can't use two unknowns to solve the equation. We need to explain why,
Plus a few tons

Let the first be x and the second be 5.7-x
（1-3/4）X +（1-3/5）（5.7-X）=（1-1/5）X
The first is 2.4 tons, and the second is 3.3 tons

The inverse function of the function y = 1 + log3 base x true number (1 ≤ x ≤ 3) is?

Firstly, the range of the original function is determined as 0 ≤ y ≤ 1
Y-1 = log3 base x true
Then put both sides of the equation on the exponent of 3 at the same time, that is: 3 ^ (Y-1) = 3 ^ (log3 base x real number)
The right part of the equation is X
To sum up, y = 3 ^ (x-1) (0 ≤ x ≤ 1)

There are 20 male employees, 16 female employees and 12 over 30 years old in a company?

50%

2x-3 = y, xy = 2009, find XY
X=?Y=？ Wrong, xy = 209

y=2x-3
Then xy = 2x ^ 2-3x = 2009
x^2-3x/2=2009/2
x^2-3x/2+9/16=2009/2+9/16
(x-3/4)^2=16081/16
x-3/4=±√16081/4
x=(3±√16081)/4
y=2x-3
therefore
x=(3-√16081)/4,y=(-3-√16081)/2
x=(3+√16081)/4,y=(-3+√16081)/2

The sixth grade students of Guangming primary school who have reached the "national physical exercise standard" account for 7 / 9 of the total number of students in the grade. 3 / 7 of them are girls, and what percentage of the total number are boys?

22 / 63 or 4 / 9

1. Given 2x + y = 2 (x, y are positive real numbers), then the value range of x ^ 2 + y ^ 2 is 2. M + n = 1, then the minimum value of m ^ 2 + n is

1. X ^ 2 + y ^ 2 represents the square of the distance from a point to (0,0), that is, the square of the distance from the point on the line segment 2x + y = 2 to (0,0), so the nearest point is the vertical point, the distance is 2 / √ 5, and the farthest point is the end point of the line segment (0,2), so the value range of x ^ 2 + y ^ 2 is [4 / 5,4]
2, m ^ 2 + n = m ^ 2 + 1-m = (m-0.5) ^ 2 + 0.75, belonging to [0.75, positive infinity]

Operation and simplification of logical expression