Question Number 78233 by jagoll last updated on 15/Jan/20
$${given}\:\mathrm{5}{x}+\mathrm{22}{y}=\mathrm{18} \\ $$$${find}\:{for}\:{x},{y}\:{integer} \\ $$
Commented by mr W last updated on 15/Jan/20
$${x}=−\mathrm{22}{k}+\mathrm{8} \\ $$$${y}=\mathrm{5}{k}−\mathrm{1} \\ $$$${with}\:{k}={any}\:{interger} \\ $$
Commented by jagoll last updated on 15/Jan/20
$${why}\:−\mathrm{22}{k}+\:\mathrm{8}\:{sir} \\ $$
Commented by jagoll last updated on 15/Jan/20
$${not}\:−\mathrm{22}{k}+\mathrm{18}?\:{sir} \\ $$
Commented by mr W last updated on 15/Jan/20
$${please}\:{read}\:{the}\:{complete}\:{Q}\mathrm{19198}. \\ $$
Commented by jagoll last updated on 15/Jan/20
$${for}\:{k}\:=\:\mathrm{0}\: \\ $$$${x}=\mathrm{8}\:,\:{y}\:=\:−\mathrm{1}\:\Rightarrow\mathrm{5}×\mathrm{8}+\mathrm{22}\left(−\mathrm{1}\right)=\mathrm{40}−\mathrm{22}\:=\:\mathrm{18}.\:{right}\:{sir} \\ $$
Commented by jagoll last updated on 15/Jan/20
$${ok}\:{sir}.\:{i}\:{will}\:{read}\: \\ $$
Commented by mathmax by abdo last updated on 15/Jan/20
$${solution}\:{in}\:{Z}^{\mathrm{2}} \:\:{we}\:{consider}\:{congruence}\:{modulo}\:\mathrm{5}\:\:\left({Z}/\mathrm{5}{Z}\:{is}\:{corps}\right) \\ $$$$\left({e}\right)\:\Rightarrow\overset{−} {\mathrm{5}}\overset{−} {{x}}\:+\mathrm{2}\overset{−} {\mathrm{2}}\:\overset{−} {{y}}=\mathrm{1}\overset{−} {\mathrm{8}}\:\Rightarrow\mathrm{0}\:+\mathrm{2}\overset{−} {{y}}=\overset{−} {\mathrm{3}}=\left(−\mathrm{2}\overset{−} {\right)}\:\Rightarrow\overset{−} {{y}}=\left(−\mathrm{1}\overset{−} {\right)}\Rightarrow \\ $$$${y}=−\mathrm{1}+\mathrm{5}{k}\:\:\:\left({k}\:{integr}\right)\:\Rightarrow\mathrm{5}{x}=\mathrm{18}−\mathrm{22}\left(−\mathrm{1}+\mathrm{5}{k}\right)\:=\mathrm{18}+\mathrm{22}−\mathrm{110}{k} \\ $$$$=\mathrm{40}−\mathrm{110}{k}\:\Rightarrow{x}\:=\frac{\mathrm{40}−\mathrm{110}{k}}{\mathrm{5}}\:=\mathrm{8}−\mathrm{22}{k}\:\Rightarrow \\ $$$${S}\:=\left\{\left(\mathrm{8}−\mathrm{22}{k},−\mathrm{1}+\mathrm{5}{k}\right)\:/{k}\:\in{Z}\right\} \\ $$$$ \\ $$
Commented by TawaTawa last updated on 15/Jan/20
$$\:\:\mathrm{5x}\:+\:\mathrm{22y}\:\:=\:\:\mathrm{18} \\ $$$$\mathrm{Compare}\:\mathrm{with}:\:\:\:\:\mathrm{ax}\:+\:\mathrm{by}\:\:=\:\:\mathrm{n} \\ $$$$\mathrm{a}\:\:=\:\:\mathrm{5},\:\:\:\mathrm{b}\:\:=\:\:\mathrm{22},\:\:\:\:\mathrm{n}\:\:=\:\:\mathrm{18} \\ $$$$\mathrm{d}\:\:=\:\:\mathrm{gcd}\left(\mathrm{5},\:\mathrm{22}\right)\:\:=\:\:\mathrm{1} \\ $$$$\therefore\:\:\:\:\:\mathrm{Integer}\:\mathrm{solution}\:\mathrm{of}\:\:\:\:\mathrm{5x}\:+\:\mathrm{22y}\:\:=\:\:\mathrm{18} \\ $$$$\:\:\mathrm{x}_{\mathrm{0}} \:\:=\:\:\mathrm{8}\:\:\:\:\:\mathrm{and}\:\:\:\mathrm{y}_{\mathrm{0}} \:\:=\:\:−\:\mathrm{1} \\ $$$$\mathrm{Therefore}, \\ $$$$\:\:\:\:\:\:\:\mathrm{General}\:\mathrm{solution}: \\ $$$$\mathrm{x}\:\:\:=\:\:\mathrm{x}_{\mathrm{0}} \:−\:\frac{\mathrm{bk}}{\mathrm{d}}\:\:\:\:\:\:\:\mathrm{and}\:\:\:\:\:\:\:\mathrm{y}\:\:=\:\:\mathrm{y}_{\mathrm{0}} \:+\:\frac{\mathrm{ak}}{\mathrm{d}} \\ $$$$\therefore\:\:\:\:\:\mathrm{x}\:\:\:=\:\:\mathrm{8}\:−\:\frac{\mathrm{22k}}{\mathrm{1}}\:\:\:\:\:\:\:\mathrm{and}\:\:\:\:\:\:\:\mathrm{y}\:\:=\:\:−\:\mathrm{1}\:+\:\frac{\mathrm{5k}}{\mathrm{1}} \\ $$$$\therefore\:\:\:\:\:\mathrm{x}\:\:\:=\:\:\mathrm{8}\:\:−\:\:\mathrm{22k}\:\:\:\:\:\:\:\:\mathrm{and}\:\:\:\:\:\:\:\mathrm{y}\:\:=\:\:−\:\mathrm{1}\:+\:\mathrm{5k} \\ $$$$\mathrm{with}\:\:\mathrm{k}\:\:\mathrm{be}\:\mathrm{any}\:\mathrm{integer}. \\ $$