Re: Can you help me and Solve the equation ???

The Qurqirish Dragon <qurqirishd@xxxxxxx> writes:

On May 16, 7:06 am, math_ali <math_...@xxxxxxxxx> wrote:
If I have that equation
A=D^2
and A must be positive integer
what is the probable value of D ???

Since you say the "probable" value of D, I am guessing that this is a
probability problem. That said, we need a probability distribution on
A to determine anything about D, other than the obvious (that D is the
positive or negative square-root of a positive integer). If A is
chosen uniformly at random from the positive integers, then all
possible values of D are equally likely (and the probability is
infinitesimal).

There is no such thing as "uniformly at random from the positive
integers".

If, for example, we say A is chosen by rolling two standard 6-sided
dice, then there are 22 possible values for D, with the positive and
negative square roots of 7 being most likely, at 1/12 each.

Why should the positive and negative square roots be equally likely?

If you are looking for the expected value of D, then it is 0
(regardless of the distribution of A). See if you can figure out why.
(one-word hint: symmetry)

Nonsense. It could be anywhere from +sqrt(E[A]) to -sqrt(E[A]).
The probability distribution of D is not determined by the probability
distribution of A.
--
Robert Israel israel@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia Vancouver, BC, Canada
.

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