Question Number 145336 by physicstutes last updated on 04/Jul/21
$$\mathrm{Which}\:\mathrm{of}\:\mathrm{the}\:\mathrm{following}\:\mathrm{linear}\:\mathrm{diophantine}\:\mathrm{equations}\:\mathrm{has} \\ $$$$\mathrm{positive}\:\mathrm{solutions}, \\ $$$$\mathrm{A}.\:{x}+\:\mathrm{5}{y}\:=\:\mathrm{7} \\ $$$$\mathrm{B}.\:{x}+\mathrm{5}{y}\:=\:\mathrm{3} \\ $$$$\mathrm{B}.\:{x}\:+\:\mathrm{5}{y}\:=\:\mathrm{2} \\ $$$$\mathrm{C}.\:{x}+\:\mathrm{5}{y}\:=\:\mathrm{1} \\ $$
Commented by Rasheed.Sindhi last updated on 04/Jul/21
$$\mathrm{A}.\:{x}+\:\mathrm{5}{y}\:=\:\mathrm{7} \\ $$
Commented by physicstutes last updated on 04/Jul/21
$$\mathrm{Please}\:\mathrm{sir}\:\mathrm{is}\:\mathrm{there}\:\mathrm{any}\:\mathrm{quik}\:\mathrm{way}\:\mathrm{to}\:\mathrm{figure}\:\mathrm{that}\:\mathrm{out}? \\ $$
Commented by mr W last updated on 04/Jul/21
$${x}\geqslant\mathrm{1},\:{y}\geqslant\mathrm{1} \\ $$$${x}+\mathrm{5}{y}\geqslant\mathrm{1}+\mathrm{5}×\mathrm{1}=\mathrm{6} \\ $$$$\Rightarrow{only}\:{x}+\mathrm{5}{y}=\mathrm{7}\:{fulfills}\:{this}! \\ $$
Commented by physicstutes last updated on 04/Jul/21
$$\mathrm{wow}\:\mathrm{thank}\:\mathrm{you}\:\mathrm{sir} \\ $$