Question

7х+у=9
5х+2у=9
Решите пж

Answer 1

7х + у = 9    // * ( - 2)
5х + 2у = 9

- 14x  - 2y = - 18
5x + 2y = 9 
===============
-  14x + 5x = - 18 + 9
- 9x = - 9 
x = 1 

y = 9 - 7 = 2 

ОТВЕТ:
( 1; 2)

Answer 2

$left { {{7x+y=9/*(-2)} atop {5x+2y=9}} right. left { {{-14x-2y=-18} atop {5x+2y=9}} right. \ -9x=-9 \ x=1 \ 5+2y=9 \ 2y=9-5 \ 2y=4 \ y=2 \ left { {{x=1} atop y=2}} right.$