Question

Rezolvati prin metoda substitutiei urmatoarele sisteme:
{2(x+y)-3y=-11
{-4x+3(x+y)=18

Answer 1

{2x+2y-3y = -11.
{-4x+3x+3y = 18 <=>

{2x -y = -11
{ -x+3y =18 <=>

{-y = -11-2x / inmultim cu -1
{-x +3y =18. <=>

{y= 11 +2x
{ -x + 3 ( 11 +2x ) = 18. <=>

{y = 11 +2x
{ -x +33 + 6x = 18 <=>

{y = 11 +2x
{ 5x = -33+18 <=>

{ y= 11 +2x
{x = -15:5 <=>

{y= 11 + 2*(-3)
{x=-3 =>. x= -3 si y = 5