What are all positive integer solutions of the bivariate linear equation 2x + 5Y = 30

What are all positive integer solutions of the bivariate linear equation 2x + 5Y = 30

2x=30-5y=5(6-y)
So x is a multiple of five
Y = (30-2x) / 5 is a positive integer
So y = (30-2x) / 5 > = 1
30-2x>=5
x

There are two towns a and B beside the road. A goes from a to B by bike. After one hour and 30 minutes, B goes from a to B by motorcycle. It is known that a's speed is 30 per hour
Km, B's speed is 80 km per hour, and it is 1 hour earlier than A. find the distance between a and B

Before the departure of Party B, the distance between Party A and Party B
30 × 1.5 = 45 (km)
The distance between the two cars from B to B
30 × 1 = 30 (km)
Car B travels 80-30 more than car a per hour = 50 (km)
Then car B starts from a to B
（30×1.5+30×1）÷（80-30）
=75÷50
=1.5 (hours)
The distance between the two places is
1.5 × 80 = 120 (km)

How to quickly memorize the square of natural number within 20

When we were in high school, our teacher asked us to remember it as a doggerel, which is the same as the multiplication formula we learned in primary school
Practice makes perfect.

The distance between the two places is 96 kilometers. A and B run from the two places at the same time and meet each other in 45 hours?

96 △ 45-54, = 120-54, = 66 km; a: car B travels 66 km per hour

If the real numbers a and B are opposite to each other, then a + B = if the real numbers a and B are opposite to each other, then ab=

If the real numbers a and B are opposite to each other, then a + B = 0
If the real numbers a and B are opposite to each other, then a = - B, ｜ AB = - B & sup2; or AB = - A & sup2;

There are two piles of coal, 94 tons in pile a and 138 tons in pile B, each carrying 9 tons a day______ Three days later, the remaining coal in pile B is three times that in pile a

（94-9x）×3=138-9x        282-27x=138-9x    282-27x+27x=138-9x+27x        282-138=138+18x-138        144÷18=18x÷18              X = 8 A: after 8 days, the remaining coal in pile B is three times that in pile a

What is the minimum value of 1 / x + 9 / y = 1, x + 2Y?

Because 1 / x + 9 / y = 1
So x + 2Y = (x + 2Y) * (1 / x + 9 / y) = 19 + 2Y / x + 9x / Y "19 + 6 times root 2, if and only if 2Y / x = 9x / y, the equal sign holds
So the minimum value of X + 2Y is the root 2 of 19 + 6 times

A batch of coal was transported by car a and car B. car a transported 30% of the coal first, and the rest was distributed to car a and car B according to the ratio of 2:5. When the transportation was finished, car a and car B transported 30 tons of coal in total
How many tons?

A batch of coal was transported by car a and car B. car a transported 30% of the coal first, and the rest was distributed to car a and car B according to the ratio of 2:5. After transportation, car B transported 30 tons of coal. How many tons of coal was this batch originally?
30 ÷ [(1-30%) × (5 / 7)] = 60 (ton)

1: It is known that KX ^ 2-2x + k is always positive for any real number x, and the value range of real number k is obtained
2: It is known that the solution of the inequality KX ^ 2 - (k ^ 2 + 1) x-3 ＜ 0 about X is - 1 ＜ K ＜ 3. Find the value of K

1. When k = 0, it is not always positive
When k ≠ 0,
k>0.①
△=4-4k²1
2. The solution should be - 1 < x < 3
-1 and 3 are two parts of the equation KX ^ 2 - (k ^ 2 + 1) x-3 = 0
∴-1+3=(k²+1)/k.①
-1×3＝-3/k.②
The solution is k = 1

The distance between the two places is 240km. The passenger cars and freight cars start from the two places at the same time and travel in opposite directions for 2.4 hours. The known speed ratio of the passenger cars and freight cars is 3:2. How many kilometers have they traveled at the meeting time?

240×3/(3+2)
=240×3/5
=144 km
A: the bus has traveled 144 kilometers