This is a proof based problem added for learning purposes and does not accept submissions.
You can view the solution by clicking on the solution tab.
You can view the solution by clicking on the solution tab.
নিচের সমীকরণটির সকল সম্ভাব্য অঋণাত্মক পূর্ণসাংখ্যিক সমাধান $(x,y)$ নির্ণয় করোঃ
$$ x! + 2^y = (x+1)!$$
দ্রষ্টব্যঃ $x! = x\cdot (x-1)!$ and $0! = 1$. উদাহরণস্বরুপ, $5! = 5\times 4\times 3\times 2\times 1 = 120$।
$x! + 2^y = (x+1)! $
$ \implies 2^y = (x+1)\cdot x! - x!$
$ \implies 2^y = x\cdot x!$
Now, if $x>2$, $3 \mid x\cdot x!$. But $3\nmid 2^y$. $\therefore x \leq 2$. $x=0$ doesn't work because $2^y = 0$ has no solutions.
By putting $x=1,2$, we obtain that $(x,y)=(1,0),(2,2)$ and we are done.