X2 − − + 3 X 4 2 X2− + = 3 X 11 0 ; 2) X2− 5 X + = + 4 X 4+ + =  + =XY X Y− + =X X

1) x

2

− − + 3 x 4 2 x

2

− + = 3 x 11 0 ; 2) x

2

5 x + = + 4 x 4

+ + =

  + =

xy x y

− + =

x x