Mathematics

Problem

If the system of equations

x - ky - z = 0,\; kx - y - z = 0

and

x + y - z = 0

has a non zero solution, then the possible values of

k

are (a) -1, 2 (b) 1, 2 (c) 0, 1 (d) -1, 1 (a) -1, 2 (b) 1, 2 (c) 0, 1 (d) -1, 1