Menu Close

a-and-b-are-distinct-primes-and-x-y-0-1-2-What-is-the-number-of-divisors-common-to-the-numbers-a-x-b-y-and-a-y-b-x-




Question Number 27888 by Rasheed.Sindhi last updated on 16/Jan/18
 a and b are distinct primes and  x,y∈{0,1,2,...}.  What is the number of divisors  common to the numbers (a^x b^y )  and (a^y b^x )?
$$\:\mathrm{a}\:\mathrm{and}\:\mathrm{b}\:\mathrm{are}\:\boldsymbol{\mathrm{distinct}}\:\boldsymbol{\mathrm{primes}}\:\mathrm{and} \\ $$$$\mathrm{x},\mathrm{y}\in\left\{\mathrm{0},\mathrm{1},\mathrm{2},…\right\}. \\ $$$$\mathrm{What}\:\mathrm{is}\:\mathrm{the}\:\boldsymbol{\mathrm{number}}\:\boldsymbol{\mathrm{of}}\:\boldsymbol{\mathrm{divisors}} \\ $$$$\boldsymbol{\mathrm{common}}\:\mathrm{to}\:\mathrm{the}\:\boldsymbol{\mathrm{numbers}}\:\left(\boldsymbol{\mathrm{a}}^{\boldsymbol{\mathrm{x}}} \boldsymbol{\mathrm{b}}^{\boldsymbol{\mathrm{y}}} \right) \\ $$$$\boldsymbol{\mathrm{and}}\:\left(\boldsymbol{\mathrm{a}}^{\boldsymbol{\mathrm{y}}} \boldsymbol{\mathrm{b}}^{\boldsymbol{\mathrm{x}}} \right)? \\ $$
Commented by prakash jain last updated on 16/Jan/18
2^(min(x,y)+1)
$$\mathrm{2}^{\mathrm{min}\left({x},\mathrm{y}\right)+\mathrm{1}} \\ $$
Commented by Rasheed.Sindhi last updated on 16/Jan/18
Thanks Sir! Any process?  Why 2 is involved?
$$\mathrm{Than}\Bbbk\mathrm{s}\:\mathrm{Sir}!\:\mathrm{Any}\:\mathrm{process}? \\ $$$$\mathrm{Why}\:\mathrm{2}\:\mathrm{is}\:\mathrm{involved}? \\ $$
Commented by Rasheed.Sindhi last updated on 17/Jan/18
Ok Sir!
$$\mathrm{Ok}\:\mathrm{Sir}! \\ $$
Commented by prakash jain last updated on 17/Jan/18
2^(min(x,y)+1)  is wrong it should  have been (min(x,y)+1)^2 .
$$\mathrm{2}^{\mathrm{min}\left(\mathrm{x},\mathrm{y}\right)+\mathrm{1}} \:\mathrm{is}\:\mathrm{wrong}\:\mathrm{it}\:\mathrm{should} \\ $$$$\mathrm{have}\:\mathrm{been}\:\left(\mathrm{min}\left(\mathrm{x},\mathrm{y}\right)+\mathrm{1}\right)^{\mathrm{2}} . \\ $$
Answered by mrW2 last updated on 17/Jan/18
Commented by Rasheed.Sindhi last updated on 17/Jan/18
Quite Ok Sir! THANKS-a-LOT!
$$\mathrm{Quite}\:\boldsymbol{\mathrm{Ok}}\:\mathrm{Sir}!\:\mathcal{THANKS}-{a}-\mathcal{LOT}! \\ $$

Leave a Reply

Your email address will not be published. Required fields are marked *