[Archive!] Pure mathematics, physics, chemistry, etc.: brain-training problems not related to trade in any way - page 205

 
Mathemat >>:

2 TheXpert: "e^х - х^e >= 0 при х > 0" - это, очевидно, придется доказать.

e^x > x^e

x > e*ln(x), x > 0

x - e*ln(x) > 0, x > 0

f(x) > 0, x > 0, f(x) = x - e*ln(x).

f'(x) = 1 - e/x = 0, x = e

f(e) = 0, f(1) = 1, f(e^2) = e(e - 2) => f(e) -- min = 0, => f(x) >=0, x > 0.

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x = sqrt(x^x)

 

Zachod, Andrei!

x = sqrt(x^x)

Is this a non-trivial solution?

 
Is there only one non-trivial formula?
 

I have one, and it does seem to describe all the solutions. But I haven't proved that yet. And I don't remember how it works yet (I picked it up by accident, something is still in my memory).

 

Mathemat писал(а) >>

Is that a non-trivial solution?

Yes. And the expression itself would look like this: (x^x)^x = x^(x^2);

Hence x^x = x^2.

 
Richie >>:

vegetate, одна великая страна так и не нашла в другой маленькой стране химическое оружие, хотя пол планеты "убедила" в том,

что оно там есть. Могу продолжить, привести и другие примеры глобального вранья, но не буду.

-

Так, что там с расходом топлива, можно подробнее вашу точку зрения.

Я лично утверждаю, что данный аппарат не взлетел бы с Луны.

Table 3: Apollo lunar module weights.

Landing stage
Take-off stage
Construction dry weight, kg
1725
1907
Main FRE fuel, kg
8172
2361
Reactive control system fuel, kg
-
284
Oxygen, kg
-
23
Water, kg
167
42
Helium, kg
19
10
Total, kg
10083
4627

Nominal weight of the lunar vehicle 14,710 kg.


Read on for yourself.

 
TheXpert >>:

Да. А само выражение будет выглядеть так: (x^x)^x = x^(x^2);

Отсюда x^x = x^2.

Well if x^x = x^2, then x=2? Then it would be 2^4 = 4^2. Or did I misunderstand something again?

P.S. The parametrization there is non-trivial, you can't take it offhand.

 

9th grade, though:)))

 
vegetate писал(а) >>

Then do the math for yourself.

I have counted before and not only me, although I had different data. But, this data is "good" too.

 
it is even better to count a>1, so that there are fewer questions