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

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

Mean inequality formula
If the root sign 3 is the equal middle term of 3 ^ A and 3 ^ B, then the minimum value of 1 / A + 1 / B is?

The root sign 3 is the equal proportion of 3 ^ A and 3 ^ B, so 3 ^ (a + b) = 3 A + B = 1
1 / A + 1 / b = a + B / AB = 1 / AB has the mean value theorem a + B ≥ 2 √ ab ≤ 1 / 4, so the minimum value of the original formula is 4

A and B vehicles with the same load carry a total of 392 tons of goods at the same time. A vehicle transports goods once every 8 hours, B vehicle transports goods once every 6 hours, and B vehicles carry% d
Use the equation. In addition, it should be easy to understand
You may not understand what I said. We need to use the equation

Let a transport x tons, B transport 392 - x tons
If their primary load is t ton, the equation can be formulated as follows
(X/T)*8=[(392-X)/T]*6
(8X)/T=[6(392-X)]/T
The result is: 8x = 6 (392-x)
8X=2352-6X
8X+6X=2352
14X=2352
X=168
B is 392-168 = 224

A basic inequality of higher one
If x > 0, the maximum value of X √ 1-x & sup2; is X=

Using the formula XY ≤ (X & sup2; + Y & sup2;) / 2
X√(1-X²)≤{X²+[√(1-X²)]²}/2={X²+1-X²}/2=1/2

The passenger and freight cars start from two places 240km apart at the same time and run in opposite directions. After meeting for 1 hour and 30 minutes, it is known that the freight car runs 10 kilometers less than the passenger car per hour. The speed of the passenger and freight cars is calculated

And 160
Freight car 75 passenger car 85

The vector a = (1,2) B = (2, y) is known. If the absolute value of B is 2, then what is the value of X and (a + XB) is perpendicular to B

|B | = √ 2 square + y square = 2
4 + y square = 4
y=0
a+xb
=(1,2)+(2x,0)
=(2x+1,2)
(a + XB) perpendicular to B
That is, 2 × (2x + 1) + 0 = 0
2x+1=0
x=-1/2

There are two kinds of apples, one is 10 kg more than the other. How many kg can be taken out of the apple
If you put it in Box B, the apples in Box B will be 3kg more than those in box A. thank you!

(10 + 3) △ 2 = 6.5kg

In English, what day of the week, what day of the month, and the order of the time?
For example, "November 15, Monday, seven o'clock."?

Time, week, month, day
at seven on Monday,November the fifteenth

A and B drive from a to B at the same time. Car a travels 120 kilometers per hour, while car B travels 100 kilometers per hour. How many hours does it take when the two cars are 80 kilometers apart?

It takes four hours when the two cars are 80 km apart

Given that the degree of three internal angles of a triangle is x, 2x and 3x respectively, the shape of triangle ABC is

X + 2x + 3x = 180 ° x = 30 ° 3x = 90 ° right triangle