Question

{3x+y=9
{x-2y=8
Решите систему уравнений ​

Answer 1

Ответ:

$\left \{ {{3x+y=9} \atop {x-2y=8}} \right. =>\\-\left \{ {{3x+y=9} \atop {x-2y=8}|*3} \right. \\(3x+y)-3(x-2y)=9-3*8\\7y=-15\\y=-\frac{15}{7} \\3x+(-\frac{15}{7} )=9\\x=\frac{26}{9} \\OTBET: x=3\frac{5}{7} ; y=-2\frac{1}{7}$