Question

Sa se afle nr. nat. x si y astfel incat   
3x+2y=41 si x+y=18

Answer 1

3x+2y=41

x+y=18
x=18-y

3(18-y)+2y=41
54-3y+2y=41
-y=41-54
-y=-13
y=13

x=18-13
x=5

Answer 2

$\left \{ {{3x+2y=41} \atop {x+y=18}} \right.$

inmultim cu -3 in a doua ecuatie

$\left \{ {3x+2y=41} \atop {-3x-6y=-54}} \right.$


se simplifica 3x cu - 3x si ⇒ -y=-13
deci y=13
18-3=5(x)