Question

Rezolvati prin metoda recducerii si substitutiei
$\left \{ {{5x-y=17} \atop {-9x+8y=19}} \right.$

Answer 1

REDUCERE
5x-y=17  l·8
-9x+8y=19

40x-8y=136
-9x+8y=  19
__________
31y  /  =155 =>y=155/31=5

 5x-y=17 l·9
-9x+8y=19 l·5

45x-9y=153
-45x+40y=95
___________
   /     31y=248 =>y=8

SUBSTITUTIE
Din prima ecuatie y=5x-17
-9x+8(5x-17)=19
-9x+40x-136=19
31x=155 =>x=5

5·5-y=17
25-y=17 =>y=8