Question

calculati y+z stiind ca x-3y+z=-8 si 2x-5y+3z=6

Answer 1

x-3y+z=-8 ⇔2x-6y+2z=-16
2x-6y+2z-2x-(-5y)-3z=-16-6=-22 ⇔
-y-z=-22 ⇔-(y+z)=-22 ⇒y+z=22 ;

Answer 2

x - 3y + z = - 8       si        2x - 5y + 3z = 6
↓
x = 3y - z - 8   inlocuim ...
   2(3y - z -8) - 5y +3z = 6
  6y - 2z - 16 - 5y + 3z =6 (restrangem termenii asemenea si ordonam ecuatia !) 
 ----   ==         ----   ==
    y +z = 6 + 16 = 22