Системы уравнений: 1) (x+y)y=12 x-3y=-8 2) 2x+y^2=5 4x+3y=5

   1)

• (x + y)y = 12;
  x - 3y = -8;
• (3y - 8 + y)y = 12;
  x = 3y - 8;
• (4y - 8)y = 12;
  x = 3y - 8;
• (y - 2)y = 3;
  x = 3y - 8;
• y^2 - 2y - 3 = 0;
  x = 3y - 8;

• D/4 = 1 + 3 = 2^2;
• y = 1 2;

• [y = -1;
  [x = 3 * (-1) - 8;
  [y = 3;
  [x = 3 * 3 - 8;
• [y = -1;
  [x = -11;
  [y = 3;
  [x = 1.

   2)

• 2x + y^2 = 5;
  4x + 3y = 5;
• 4x + 2y^2 = 10;
  4x = 5 - 3y;
• 5 - 3y + 2y^2 - 10 = 0;
  4x = 5 - 3y;
• 2y^2 - 3y - 5 = 0;
  x = 5/4 - 3y/4;

• D = 3^2 + 4 * 2 * 5 = 49 = 7^2;
• y = (3 7)/4;
• y1 = (3 - 7)/4 = -1;
• y2 = (3 + 7)/4 = 5/2;

• [y = -1;
  [x = 5/4 + 3/4;
  [y = 5/2;
  [x = 5/4 - 3/4 * 5/2;
• [y = -1;
  [x = 2;
  [y = 5/2;
  [x = -5/8.

   Ответ:

• 1) (-11; -1), (1; 3);
• 2) (2; -1), (-5/8; 5/2).