If 5x-4y = 0 and XY ≠ 0, then x: y = 0

If 5x-4y = 0 and XY ≠ 0, then x: y = 0

5x=4y
x:y=4:5

There are 102 interest groups in a primary school, 125 more boys than girls. How many boys and girls are there?

Answer: there are 52 boys and 50 girls

Can the number in the square root be equal to 0

The number in the square root can be zero
In the range of real numbers, the number in the square root sign, that is, the number to be squared, cannot be negative
In the plural, there is no such requirement

There are 90 books in group A, B and C. if group B borrows three books from group A and then gives five books to group C, the number of books in the three groups is the same. How many books did group A, B and C have?
It's better to have a line diagram

90 △ 3 = 30
A: 30 + 3 = 33
B: 30 + 5-3 = 32
C: 30-5 = 25

If the division quotient of two nonnegative numbers is positive and the sum of two numbers is nonnegative, then two numbers are negative

This question is (positive number, 0, negative number) the division quotient of two non negative numbers is positive = both numbers are positive (not 0) the sum of two numbers is non negative = (this sentence is nonsense, useless) so the result is: then both numbers are positive

If the ratio of a to B is 3:4 and the ratio of B to C is 6:7, then a: B: C = (): ()
、、

This question is about the ratio of a, B and C. the two conditions given in the question include a, B and C respectively, but the proportion of the same B is different. So we should unify the proportion of B in the two conditions, that is, find the least common multiple of 4 and 6, 12, then the ratio of a and B is 3:4 = 9:12, the ratio of B to C is 6:7 = 12:14

If the equation cos2x + 2sinx + a = 0, then the range of a
If the equation cos2x + 2sinx + a = 0 has a real solution, then the range of a is not calculated

For such a problem, we first change it into a function of the same name, the original formula = cos2x + 2sinx + a = 1-2 (SiNx) ^ 2 + 2sinx + a (let t = SiNx) = - 2T ^ 2 + 2T + 1 + A, so the original problem and the equation about t - 2T ^ 2 + 2T + 1 + a = 0 have real number solutions on [- 1,1], and the problem of finding the range of a is also related to t

45% of a number is equal to 2 / 5 of 60?

This number is X
45%x=60x2/5
9/20x=24
x=24x20/9
x=160/3

A cubic equation is solved, x-2y = - 9, Y-Z = 3, 2Z + x = 47;

x-2y=-9 (1)
y-z=3 (2)
2z+x=47 (3)
From (2) we get y = Z + 3
Substituting (1)
x-2z-6=-9
x-2z=-3 (4)
（4）+（3）
2x=44
x=22
（3）-（4）
4z=50
z=25/2
y=z+3=31/2

A batch of parts can be processed in 20 days by Party A alone and 30 days by Party B alone. After several days of working together, Party B asks for leave
For a batch of parts, Party A can finish it in 20 days and Party B can finish it in 30 days. After several days of working together, Party B asks for leave, and Party A continues to do it until the parts are processed. It takes 16 days from the start to the end of parts processing, and how many days does Party B ask for leave? (equations and formulas are used) it takes a long process!

1 / 20 × 16 = 4 / 5 in 16 days
Party B completes 1-4 / 5 = 1 / 5
Then B worked (1 / 5) / (1 / 30) = 6 days
B ask for leave 16-6 = 10 days
Let B take a day off
（1/20+1/30）×（16-a）+1/20×a=1
1/12×（16-a）+1/20×a=1
80-5a+3a=60
2a=20
A = 10 days