Question

stiind ca X+4·y+2·z=13 si 3·x+2·z=11 ,  determinati X+Y+Z

Answer 1

$\left \{ {{x+4y+2z=13} *(-1)\atop {3x+2z=11}} \right. \\ \left \{ {{-x-4y-2z=-13} \atop {3x+2z=11}} \right. (+) \\ 2x-4y=-2=>x=-1+2y$
Inlocuiesti x in una dintre ecuatii si afli pe rand ceilalti termeni.