Question

Решите систему уравнений 5х-3у=9 и 3х+у=11

Answer 1

5х-3у=9

3х+у=11   /*3

 

5х-3у=9

9х+3у=33

 

5х-3у=9

14х=42

 

5х-3у=9

х=3

 

х=3

3*3-у=11

 

х=3

у=-2

Answer 2

$\displaystyle \tt \left \{ {{5x-3y=9} \atop {3x+y=11}} \right.\\\\\\\left \{ {{y=11-3x} \ \ \ \ \ \ \ \ \ \ \ \ \atop {5x-3\cdot(11-3x)=9}} \right.\\\\\\5x-33+9x=9\\14x=42\\x=3 \ \ \ \ \ \ \ \ \ \ \ \ y=11-3\cdot3=2$

Ответ: {3; 2}