1.
Let [λ][\lambda] denote the greatest integer less than or equal to λ\lambda. The set of all values of λ\lambda for which the system of linear equations
x+y+z=4,x + y + z = 4,

3x+2y+5z=3,3x + 2y + 5z = 3,

9x+4y+(28+[λ])z=[λ]9x + 4y + (28 + [\lambda]) z = [\lambda]

has a solution, is: